Maxed mechaniks in Armored Corps?

Realistically you're not going to get to repair them very often.

Shocktroopers have the highest chance to get repaired, but even then you can really only get 2 mechanics B2B with a single model in practice. So even a min unit is unlikely to be able to have every member repair something in a turn unless the damage is really spread out.

The Dragos mini feat would let you spread the damage out enough that multiple repairs could be applied, but even if they are fully repaired I wouldn't expect them to survive the next round in most situations. So spending points on more models that do damage is usually better than on models that repair damage...

The repair bonus is pretty decent on 'jacks though!

I take two minimum units but mainly for the advanced move. The repairs really are just a bonus to me.

Starting from 4pt you can take more actual mow models that do things instead of just repairing mows.

The mechs aren't great against lists that can handle AK well. High POW shooting or melee attacks can get through MoW ARM+Boxes. They're tough, but not that tough.

And as welshhoppo notes, good with Tough (and colossals). Irusk1's feat +
mechs can be very strong on attrition, especially with Iron Flesh also
in the mix. If I get one decent lot of repairs out of them, I'm happy.

But mechs are marvellous if you come up against lists with POW10/11 shooting (or, I suppose, from things like e-leaps by someone other than Nemo3, corrosion templates and the like) which try to chip away at your MoW as they advance. In that context even an individual mech can repair the damage a single MoW takes in a turn, potentially keeping your list going that little bit longer. Thanks to one of those miracles of list choice, I once ended up with Sons of the Tempest vs AK. Gunmages don't like MoW at the best of times, but even more when the shooting is repaired. Even pseudo-weaponmaster Gunmages don't do much against shield-walled STs in melee. Add in the Shocktrooper UA and there's no pushing or knockdown from Thunderbolt rounds either. More or less neutered a significant portion of the list.

I'd generally always try for 1 min unit at least, unless there is a good reason not to include them. I think I'd include one unit even if they didn't contribute to free points or advance move, but they do. My current Kozlov list even has a max unit (mainly because upgrading min to max is the only 2 point upgrade in AK, and it gets me to 3 free solos).

I think less Nightmares and more Irritants.

In any case, play in Irusk 2 if your goal is to repair Man of War, else don't bother. If you're really after Advanced Moves, there's better sources of it and those sources Do Work. Mechanics do not unless you're playing Vlad 2 and want to put in some random Transference swings for their charges. Or, credit where it's due, Last Stand from Strakhov 2. They're not even that great at running to contest with their 12/12 statline and Speed 5. Random buffs don't really change this equation much.

The list is also already rather thin on models due to its elite nature. Diluting it to include some mechanics for the express purpose of repairing your Man of War is not going to win you many favours.

Furthermore in practice repairing a Man of War is both awkward to manoeuvre around, especially for Shocktroopers (they don't get the benefits of Tactician after all) and in the grand scheme of things not super relevant. A Man of War on 1 box functions as well as one on full, plus the repair check itself is random so you're needing, what, 2+ Mechanics to guarentee a guy gets fully healed if he made a tough roll or had damage shunted to him by Dragadovich?

Furthermore Man of War do not absorb damage like a Warjack. A warjack that takes 24 damage still has 10 boxes left, is in one location on the board for your mechanics to all mob and can be refilled for 4D3+4. Concentrated repairing will get it back up to full functionality. A Man of War unit that takes 24 damage has either had 3 memebers die that you cannot repair or had the damage spread out across multiple models controlled by your opponent to a large degree, with the odd dead or tough'd model thrown in for good measure.

So no, Repairing Man of War is a waste in most cases. Irusk 2 can make it work, between universal Tactician and Tough, but even he would often rather just More Steam Mans

Instead, with mechanics, think of what they do for your Warjacks and treat any incidental Man of War fixing as an added bonus. Because the D3+1 per guy is quite fantastic on, say, a Colossal or a Chariot when you chain a bunch of repairs together. And on turns when they're bored and they get the odd bit of cheeky repairing in, treated it as an incidental synergy you get as a side show to their actual purpose.

Also the theme bonus works on Gobber Tinkers and they're still the best mechanics in the game and quite a good addition to Armoured Korps if you don't need the solo slot for someone like Ragman, Eilish or Saxon.

With Altanas you have a built-in source of tough. Now he MAY wish to hand out another battle plan (a fun and tactical choice as opposed to Joe). With the SHock UA you have steady (nothing says "F you" than no knockdown tough on ARM 21 models. You can pretty easily fit 2 mecks into the back arc of a MoW without Unduly hindering ovement (three is pushing it) and you are guaranteed 4 wounds of repair and I believe the modality of the probability curve is around 5.75.

And the Advanced move is critical in this theme.

Now THREE feels excessive unless you are doing something really janky and using chariots and tankers rather than MoW units. But I think 6 points for 2 is usually a good investment compared to lots of other options.

Finally, while tinker is great for the last 2 points, he is NOT the merc slot. That has to go to Ragman about 70%+ of the time because you really need something to help the shocks hit harder and not that many of our casters can arm and damage buff the shocks (B1, I1, Kozlov and last stand for a very expensive POW buff)