well - there's all the infantry and the av for that.
Yep just realised that, sorry
what exactly do you have in mind for the small demon engines - historically, I can only find khorne stuff which ranges from the AV blood slaughterer to the DC3 and more stuff.
I make it a minium of 15 faction specific daemon engines in the AV class, that's a lot to ignore. If you're counting deathwheels, then i recon newer things like blight drones count.
There's three variants of slaanesh knight, the nurgle contagion and a wide range of khorne (cannon, reaper, scorp, cauldron, doom, tower, slaughts * 2?). There is also discusion elsewhere on taccom about creating some non-TS tzeentch engines, assuming you're keeping towers out of it. Doomwings are tzeentch AV deamon engines, it seems odd to include them by name and exclude all other faction specific AV daemon engines.
'Historically' does not really matter, the way the list has been done with marks and upgrades instead of naming specific units (eg, plague tower) gives scope for people to make their own, in a addition to the 12 oldschool (15+? with newer GW additions) AV faction engines.
I see that your list aim does specifically say focus on medium sized engines, so that's fine, i just feel your missing out a big chunk of smaller canon daemon engines and wondered why. They don't need to be the focus of the list, but you've got a BIG engine in there, so why not the smaller ones?