Ehhr, that’s the thing, let me walk you through all that I’ve gather up so far:
Firstly, direct to the point, I don’t think it would be impossible to conjecture a composition that would be OP without the cap. You give me one that can be microed with 12 units selected at once and from there we can make some assumptions. Is it too strong? Is it too easy to control? Adding even more units should only amplify these characteristics.
No one gave me anything. There was one guy talking about how it would look like "blob armies" of SC2 and I tried this with 12 Wind Riders/Gargoyles. It doesn’t come close to SC2, the turn rates and attack animations are so far apart that I was almost laughing when my attempts to stutter step failed miserably (I can do that ok-ish in SC2 and MOBAs).
So if you hope to reliably control all your army with one single static control group, I think you will get rekt, and that already happens with the 12 cap. You must dictate what each small group or even what each single unit must do during an engagement at high level. There is no easy way out.
Furthermore, there was the claim that army compositions are dictated at least a bit by the 12 cap, but how come a pro player like Grubby say that increasing the cap to 14 or 16 would probably be fine? At least that he would have in mind.
Then there is the claim that the too many units selected at once would create paging at the Unit Selection UI. Which is true and I expect real though from the team to implement it properly if they decide to remove the cap, but then it hitted me: This would only happen if you are already selecting more than 12 units, this naturally happens right now when you try to box select and select more than the cap, but it’s worse, since you can’t even page, you must attempt to select your units again and aim for less of then (which can still be done with unlimited selection if your mouse is faster than your paging skills).
And there is the idea that it is an important tool to make new players learn the game, but that transition - from the noob who wants to blindly play in their own noob way, to the good player that tries to get better after each game and looks for online help and such - it is obvious that in 2018 it is an internal effort and we have all the material necessary to the players looking to improve (with more to come probably). We already play the game much further than the expectations of the original designers, we don’t need training wells anymore. We can leave noobs and beginners alike play at their own pace.
Finally, if I haven’t forgot anything, there is the very basic purist idea to follow: the game shouldn’t change. I think this idea, at least conceptually, is really important. I think no change should go without thought and the fear to break this game is commendable. But I can’t keep my own purist feelings in the face of a change that will help new players, transitioning players, and give us all comfort too. This to me is exactly like the Hotkeys issue I’ve seen in SC:R were people were advocating that the Probe Hotkey on P was part of the balance. Giving commands shouldn’t be hindered mechanically, this should be hindered by a players own skill, this is the essence of micro.