I need make up few units more: ballistas, trebuchets, and wyverns. What game statistics do you recommend for first 2?
Go with the LOTR specs and adjust according to effect you want to achieve.
Wyverns could be little tricky. Guess I'll tick helicopter movement. It is said .50 caliber weapons can drop them with armor piercing rounds. So I guess I just copy Mi-24's DF value for that...? For AP value I think I could just use 72 of flamethrower tanks. I think I should make wyverns slower than regular helicopters. Any ideas how?
Yes. You are going where no scenario designer has gone before. This is why I am the only one stupid enough to try to help. I don't think there is any way to make helicopters slower. Have you tried giving them walking speed? You can adjust their range though.
I noticed something odd with flamethrower tanks: those have AT values at 0. When tanks were burned with molotov cocktails, shouldn't flamethrowers make some number as well? Works in tactical scale wargames too: Steel Panthers (the original at least) and Combat Mission 2.
The equipment database is what it is. It is based upon the operational assessment of the equipment in question. Not aware that flamethrower tanks were noted as an operational anti-tank option.
Other weird things I have noticed:
All helicopters have AA values at 0 like AA missiles wouldn't be available for them (does helos count as air units?)
PzKpfw III has better AP value than PzKpfw II, like 37 mm breech loaded cannon is better at anti-infantry work than pair of 20 mm autocannons. Really now?
The equipment database is what it is. It is based upon the operational assessment of the equipment in question. Do you see helicopters going up against Migs, Falcons, Eagles? AS for the PzKpfw III having a better AP value than PzKpfw II, if you don't like it, change it.
Best wishes,
Steve