I thought i would add my two cents aswell.
I played it first singleplayer, and then a few times in multiplayer before collecting my thoughts.
Caveat: My english is poor, if it seems i mean any offence, i dont, its just poor wording.
First reaction : I was suprised by the unbound movement. But after reading your post, and especially after playing in multiplayer it felt very smooth and it was a good choise!
Thoughts : Some of these thoughts/ideas might be because im bad at turn based strategy games. First of all, it was fun, but since it was a turn based strategy i felt like i needed more information to make my decisions, and that the game changed without it letting me know. I never really got the 'a-ha!" moment how to solve the problems i was facing. And sometimes it didnt feel like it mattered what i did. But again, it was fun! dont forget that! Heres my thoughts on why i felt the way i felt.
I enjoyed single player more. It was often clearer what needed to be done (eg using the explosives to kill enemies and stuff, neat!). But... I didnt realise untill far to late that the infested terran onehit kills everything. It felt like it could have been telegraphed more clearly. Then again i didnt click them and check their damage... so... my bad hah! I found that they deal 500 damage. So no amount of upgrades would help. Maybe having an aura of some sort? Maybe a model to show that theyre reaaally dangerous?
Having upgrades that are not usefull felt frustrating. Maybe giving just flat bonuses instead of %. It was really hard to work around the infested terrans, especially since there was often so many of them. We played a full lobby and it felt like a sea of enemies. It was not always clear which units the enemy would attack, and one time i thought i was safe but it moved against me instead of my ally and killed. I noticed the abilities units had was changed during the game, i felt i wanted a reason for it. Gaining new abilities feel okay, or if you change them and tell the player (During this mission, snipers have this ability). But removing abilities without telling the player? Im going to use cloak this level... Its gone. Lastly i feel like punishing a player for being a team player (dying instead of another), feel hard. When players are also rewarded for playing safe (given more minerals and even a shoutout) it felt rough to have my super armored unit just die in one shot.
I agree that some story or options for levels could have been nice.
I really like the ideas though. Having diffrent units to solve problems, abilities, and teamwork. I like the idea with co-op turn based strategy. It feels like this is gonna be very cool once its done!
Hope my feedback helps.