I think artillery models should come in the basic configuration as towed, once researched for a previous version.

In RL, with the motorization of the army, I suppose it becomes the basic mean of transportation for it.

Alternatives could be the SPGs that are in-game already.

Each level unlocks both the regular 'drawn/pack' version (which is in the infantry battalions category) and the 'towed/motorized' version (which is in the mobile category).

I missed the mechanised version as well, got used from the idea of the motorised arty original mod.

Oh, Rocket Artillery needs a research for each tank and mechanised as they were like that in WW2 put on everything.

Would you consider adding mechanised art/at/aa and rocket to mirror the real life versions of such? i.e. the US halftracks with the quad 50. cal turret or the German halftracks with at guns built onto the frame and the walking stuka or mortar half-tracks?

Thats an interesting thought. Do you think these should be available instantly if you have Mech + Art/AA/AT or be a subtech/sidetech to unlock them (maybe just 1 for all of them?)

Sims_docs idea of armored SP rocketarty is also something I will look into as soon as I have the AI beated into somewhat better shape.

I think it should be like the variants of tanks, Something you research with the little icon however those icons are often hard to see.

Perhaps have the mech variants available following research of the APC, perhaps as a subtech. For example have a branch leading from the first APC tech to a tech labled "Mechanise the Army" or some-such but have the tech itself placed around the 42 mark for research purposes.

Sims_doc's idea is one I like the sound of quite a bit though to my knowledge the only rocket armed tanks were the Sherman Calliope and captured Hotchkiss (I think) light tanks given walking stuka launchers.