Should I Re-Enlist?

I dunno, personally I find the game is moving too fast for me to keep up with now, what with all the CID and whatnot. Trying to build a competitive list without spending money when you don't have any releases from the last 6 years might be tough.

However, perhaps you could try a bit of Company of Iron to start? It's a smaller game - a unit and a couple of solos a side usually - which I think makes it easier to get into since it's less about stacking combos. Between Khador and Merc models you already have, you should be able to build a wide variety of playable COI lists.

I believe the rules are free. You do need a card deck, but only one between two players so if you find anyone else who plays they will already have the deck (of course one deck is not too pricey).

The classics (wg spam, pike spam) still work. We have jackspam now and mows will finally get a good list in June, though you probably would need some new solos and attaches for the latter one, but if you have many of them you can try to convert maybe since it's just mows with a big medal on their pauldrons anyway.

Jack Spam is nice. I have a lot of 'Jacks, even if most are older releases.

I've been around. Mostly on the Creepy Card Player II. I don't get to game much at all, not Warmachine, or any mini game, nor my tabletop RPGs nor my computer games. So sad am I.

Anyways, though I have a crudton of MoWs, I do have a fondness for the Iron Fangs, Greylords, and Cavalry. Though Mk. II tended to steer us towards Winter Guard, I just never loved them as much as some.

My favorite casters have been just about any version of Vlad (though I never played Vlad3) and Zerkova1.

Fortunately, I do have the deck. I had the version 2 of the app (and felt gypped they made me buy stuff again) as well. I just removed it a few months ago as it was taking tablet space and I've never used it.

In the effort to be economical I am suggesting waiting on the forgeseers and going with MoW and WGK as the two "themes" to start with.  He may already have the Kovnick and honestly if not you can do a conversion on the cheap (and they are fairly inexpensive).  the Shocks UA and the new Tankers are going to be more expensive - and I think you need at least 1 of each (if not 2 UAs).  Dragos and the Bomber UA can probably wait depending on builds.

OVer in WGK you only need as many rockets as you are running for units.  Probably 3 (and maybe 6) depending if we go for "fun" of a conquest and a Fun Carriage under Vlad1.

Near as I can tell doing math in my head - and assuming decent themes in January - we can get our fellow Khadorian back in the fight for under $100 out the door.  Nature of the hobby to always want to buy more to further tweek out the list but I think that gets up 90% of the way there.

I read "not going to buy solos too often" as having a VERY limited budget for gaming. $100 sounds a touch optimistic to me, at least if you consider the first few months. And like you alluded to, it's the nature of the hobby to keep spending more than you intended to.

It's not that I don't want him to get back into it, it's just that I sometimes think some players fon't realise how difficult the hobby can be for people with different circumstances, so I want to try to keep things realistic, and suggest manageable alternatives.

Hence Company of Iron. Much lower barrier to entry than Warmachine I believe, espe ially if you already have any models, while still using much of the same rules so should feel familiar. If you can find players of course.

If you're not trying to build The Most Powerful Khador Army Ever^TM, then you're probably able to get by with fairly limited investment. The Conquest helps, as it gives you a way to spend a fair chunk of points on an effective model, even in a 75 point list (Conquest will run you about 1/3 of your total points allowance).

That said:
1 - it's the nature of the industry for some new releases to be very desirable;
2 - given the way you list your collection, it sounds like you're something of a completionist (and then some - two units of Kossites!). So those first steps might end up progressing ever further...

The current game tends to use themes to design lists. Khador themes aren't caster specific anymore (some factions have themes with only some of their casters). These limit the available units and solos. Most allow mercenaries (typically a single unit and a single solo), although Winterguard Kommand does not permit character solos. Worth remembering that because of how the Partisan rules work, Kayazy units are mercenaries for theme list purposes, but then become Friendly Faction models due to the partisan rule. This is important because many buff spells and feats are now limited to friendly faction models compared to Mk2. Assassins are still a decent unit (although because Iron Flesh has changed, they're now longer unhittable killing machines). Kayazy Eliminators are almost always a nice pick if you aren't using the merc option for anything else, as they are really helpful for scenario play.

Other mercs (Nyss, for example) can be made friendly faction by including Valachev, a character UA who is a ranking officer. If you don't have him yet, adding him would be a cheap way to add a fairly hefty merc unit in theme lists. Another possibility is using him to make Aiyana & Holt friendly faction. Aiyana's damage buff became friendly faction in the Mk3 transition, so this is helpful, although A&H are often included in lists to make sure she can give a model/unit magic weapons. This was a big concern for a time because of a particular popular Cryx theme, although that theme has become less popular.

Based on what you've said, some possibilities:

Winter Guard Kommand - this can be played with lots and lots of Winterguard Rockets, or fewer. Sometimes played as a jack heavy list because one theme benefit is Advance Move for a 1 jack for each Winter Guard unit in the list. Getting Khador jacks an extra 4" up the table can be helpful. Widowmakers can be included.

I have really enjoyed Vlad1, a unit of Winter Guard infantry with the command attachment, a unit of WG Riflemen + rockets (they can take those now, that's a change for you), the Gun(Fun) Carriage and then filling the points with jacks. It's fairly flexible.

But there's plenty of options here. Someone's been running Butcher3 in this theme with the Gun Carriage too. Irusk2 always loves Winterguard. I'd consider Irusk2 + Conquest + your winterguard + Kayazy assassins with Underboss as a playable build.

Legion of Steel - the Iron Fang theme, so possibly right up your alley. Irusks can use this well, as can Zerkova1. There's one new solo for Iron Fangs (Skirova) but she shouldn't be that expensive and if you have a spare Iron Fang model and can find a female head from somewhere (you may be able to buy/trade a single head from another player), you could convert a version anyway.

Armored Korp - the Man of War theme. Just been through playtesting with various new MoW models, so we're not certain how it will turn out. But MoW are definitely playable now, in contrast to Mk2. The Shocktroopers were good before the playtest (they have a nice to have, but not essential, new UA). Hopefully the other units will turn out well. The Drakhun is not talked about that much but remains a solid piece. The MoW Kovnik is important in improving the speed of MoW units (especially the Shock troopers). Irusk1 and Irusk2 are both solid choices. The Battlebox caster, Kozlov, is also good with MoW (including Shocktroopers) so would also be a good place to start.

What isn't clear yet is quite how essential the new models which were playtested will be to the effectiveness of the theme. I was quite happily planning some MoW lists before the new models were revealed and thought the lists would be playable, so the new models probably aren't essential.

Jaws of the Wolf - Kayazy + jacks (and Widowmakers). Not the best theme out there, but if you've got lots of Kayazy and some jacks, you could try it. Strakhov1 runs it quite well.