It might be closer to be finished than you think.
I poked around in the demo out of curiosity and I remember finding what looked like the full list of status effects, among other things. If there isn't more planned, it's probably a matter of debugging and completing all the various scenes.
Though, I didn't see any traces of an "alternative suit" status effect, despite both of the Hasumi games and HACHINA having one, it would be a missed opportunity to not have one in this game. So perhaps I'm wrong and it is uncomplete.
Did I misremember or HACHINA came with some sort of english language option? Hopefully it will be the same.
The game isnt finished though, the demo might contain some data thats locked in the cutting room floor but he's not designed every enemy yet, I asked how many enemies will be in the full version and he said he isnt sure because he's not at that stage yet. I assume we'll get about 9 - 12 enemies in total and he must have done the weapons because you see empty boxes, you will probably get launchers with splash damage, maybe something like caltrops, laser weapons etc.
There will be an 'alternative suit' for definite because you even see it on a Game-Over CG, shes like in some ecchi nurse outfit and you actually see these nurses on his Ci-en page that will have the same pattern behaviour as the male combatants. I assume once you get caught by them multiple times her outfit will change and remain like that until you finish the stage. The visor works the same, if you get caught by one and after cumming more than 2/3 times the visor remains fixed to her face just like with Hasumi.
You will probably get enemies that fire projectiles back at you, maybe some that will move faster than the player.
But I dont think this game is near completion I could be wrong but a test build of Sinister 2 came out literally over a year ago and thats only getting released this month and that uses the Unity Engine too.
As for English, its likely you will get it I think both Hasumi and Hachina got official English versions but he is still undecided about Night Watch. Its a bit sketchy ATM due to DLsite censoring their games and the MC does pretty much dress like a schoolgirl