Just contemplating scripts I could make to help you all out with the summoning issue. Let me know what you think: summon_random unit1|percentage,unit2|percentage,unit3percentage (applies to skills). Percentages must add to 100. Summon random units, though the problem here is that you wouldn't be able to change the cost for the skill, unless someone can think of a way to specify the cost for each type of unit that isn't completely unwieldy. Another idea is giving all the summoning skills a special ai_random_summon script flag then overriding the AI to randomly decide which unit to summon. This is tough jus because the AI isn't fully scriptable yet, and finding a viable tile. Indeed messing with TB AI can be quite troublesome which is why I generally try not to mess with it.
Though I wish that there was a way to give AI skill precedence so that it would try to use the higher precedence skills first but sadly that's just not happening right now.
