First Impressions on BGG: https://boardgamegeek.com/thread/1617009/initial-thoughts-after-gencon-demo
Cool, thanks for that link. Looks like there are indeed classes of upgrades, the super generic icons at the tops of the preview cards (horn and banner) are in fact indicative of their category.
Looking at the types of upgrades, there are: musician, banner, leader, magic? (triple rings) and siege engine? Upgrades. the last one is clearly a ballista only available to larger units. Interesting that, curious to see if those will just be cards you stick to the unit's stack or if there will be actual models to place in the unit.
Looks a large part of the game mechanics comes from what icons are available on the units dials, much like x-wing does. But each unit has twin dials so that opens up more options I'm sure.