Here is the deal from my play through - there isn't a lot to get in the game area you are allowed to play in, in the demo. Unless I am missing something. Power armor 6-8 missiles and an energy tank.
If you are taking input for new parts to the game would be some kind of mutagen addition to allow the heroin to get additional powers, even increase energy/health levels, jump, armor and the like. (Though this seems like just surface level things, since there is no metroid flipping here.) Enemies seem a bit too Metroid-esk, Might work on differing them so that there is no conflict with Nintendo. Heroin's hair color could be changed for the same reason. Else include a hair color choice, at least for the few times she gets out of her armor to show... (Though as it is seemingly version .5 a lot of the seen features and things might change over the development... Might suggest also getting in contact with DoctorM64 the one that made AM2R and see if he can help with getting additional tallent to help this get made. )
Well, judging from your numbers, you missed 1 or 2 items depending on if you just left one key item out or not.
But that being said, it is a demo after all so of course it won't have that much content, in fact, it's already quite long for a demo in my opinion.
The main functions of the demo is to show people how the game plays and let them have a way to see if it works on their computer.
I already have A LOT of upgrades and such planned, some are in the game already (not in the demo), so I'm probably not going to be adding many suggestions like that at the moment.
Not 100% sure what "metroid flipping" means but I assume it's like the spinjump maybe? In that case, no there will not be any spinjump in this game.
I mean, sure, many enemies are based on enemies from metroid and behave very similar but it is all original sprites and code so I don't see how this would be a problem really.
Same goes for hair color.. and having the option to change it will likely not be in the game, I'd have to add a lot of extra sprites just for that.
And regarding contacting DoctorM64, I'm not really looking for any help in this regard right now (maybe not ever) so this will likely not be needed.
Thanks for trying the demo and giving feedback.