Good to see this list

Your general idea and included units mostly looks good. I disagree with Jagged, in the past IG used to have entore formations of Vanquishers but they're hard to make and some FW's that made them were destroyed so they've become rare with IG. An AM tank army would be composed of rare types though - the AM are known to keep and use the best tanks for themselves.
Various comments:
Macharius should not be in the list!!! Adeptus Mechanicus are all about using older/rarer higher technology tanks in their armies compared to guard. The background for Machariuses is that Forge World Lucius was getting over stretched by orders for superheavies and had lost the technology to produce Baneblades. Their tech priests searched and found ancient records they pieced together to make the Macharius, a replacement 'second generation Baneblade' though it took 200 years for Mars to approve the design so it could be built and ironically by that time other Tech Priests had begun production of a Lucius pattern Baneblade that was much lower tech than the true Martian Baneblade, but still a better option. Due to high demand they ended up building both however (the first Macharius production is 852.M41 or around 150 years from the end of the 40k timeline, insignifigantly new in terms of an empire around for 10,000 years). Machariuses are quicker to produce, but are clunky and low-tech.
The background is definite that other Forge Worlds like Mars, Ryza, ect which build true Baneblades don't ever build Machariuses and so wouldn't ever have them in their armies. It is known that the AM jealously guard and hoard the best technology for themselves and their armies – if Lucius is building both Lucius pattern Baneblades and Machariuses it is surely likely that they would choose to equip their armies with the better Lucius Baneblades while shipping the Machariuses out for Guard regiments. Yes, I gather some random Black Library novel had some AM with Machariuses, probably because it was a new tank release at the time and the author hadn't bothered to read the background properly, but BL novels do wacky inapropriate things at times and shouldn't be given too much weight, the core background for the unit is more important. If very occasionally a small sub-set of Forge Worlds field Machariuses with their armies out of desperation this shouldn't be represented in the core list, which should represent a typical AM Catapracti list.
Please allow the core Russ formation to be made up of Leman Russ Executioners or Vanquishers not just as an upgrade! They're another of the few tanks we know the AM use in their armies, most especially the plasma specialists of Forge World Ryza in very large numbers. As per the FW background which says “the Forge World of Ryza, whose own tech guard regiments are
almost exclusively equipped with Executioners.” In an ideal world we might have variant lists for each Forge World, but assuming that isn't going to happen then the core AM lists should be able to cater for any of the main Forge Worlds. The Epic-UK tank list allows for tank armies of LR Executioners so it's not anything unbalanced.
Spectrar Ghost wrote:
Why Valdors? They're obsolete, and the Mechanicus doesn't need obsolete tanks.
Huh? I think you're confusing them with Malcadors. Besides the AM are obsesive about old technology and keeping it alive – knowledge and technology is their religion and way of life. They have a lot of ancient technology in their armies, it's their thing.
Valdors should definitely be in the list, they're one of the very few tanks specifically stated to be used by the AM. To quote Forge World, they say the “Valdor Tank Hunter, an ancient design based on the Malcador chassis, it is built round a powerful neutron laser weapon able to make a mockery of the strongest armoured defence. Although more common in the forces of the Adeptus Mechanicus, the arcane technology used in their construction makes these tanks revered relics within Imperial Guard armoured companies.”
Should Valdors and Vanquishers be priced the same? I doubt I'd ever choose to take Vanquishers over Valdors. Ok, they don't have Heavy Bolters but Valdors have a 60cm Disrupt MW3+ main gun and 15cm move so can garrison and start on overwatch.
Why not use the
Praetor Armoured Assault Launcher for AA in the list?
The 40k model can select a few different types of missiles but the AA ones would be most appropriate for epic. The list could then have a 2DC high-tech superheavy rather than the boring option of just having to use a Hydra like the IG list. Some of us have good proxies for this unit too, but others could just proxy some kind of superheavy with AA easily enough.

Spectrar Ghost wrote:
Three Executioners would cost about 200 using the Minervan costs as a baseline.
Apart from AA and transport the Net-EA lists upgrades are mostly overcosted and hardly ever taken so shouldn't be followed too much. It's nearly always better to have more activations. Epic-UK have tried to do something about this by reducing the cost of upgrades compared to our IG and other lists e.g. 50 points for 3 add-on Griffons compared to 75 in the Net-EA.
If you're going to have the option to attach a Superheavy to a tank formation it should be cheaper not 200 points (part of the 200 pays for the separate activation). Cost it 175.
Perhaps consider having termites, moles and hellebores in the list? Perhaps these might be better saved for the Ordo Reductor siege list but we know AM use tunnellers.
OT: but I don't understand or agree with the assertion Imperators doesn't fit in 3k lists, that's not the case, at least not for the core TL list. Remember an Imperator counts as having a Corvus Assault Pod due to it's transport abilities so allows one cheap 100 point 01- per corvus Skitiarii formation to be taken (the Warmonger goes further allowing this plus a 75 point flyer) and 1350 for two formations is a lot, but it takes care of your TK and potentially the AA for the army with it's 90cm AA 4+ TKD3. It's possible to use the rest of the points to get a decent number of activations then. I don't think the Imperator is overcosted at all, it seems about right to me. I believe you complained previously Jagged because you fired most of a 5k tank army at it and it killed a lot before it died but the tactical error was trying to kill it rather than sticking one blast marker on it and ignoring and hiding from it while taking out other formations to reduce his activations.