Hello I like to make a suggestion!
I don't know much about things in games and UI but to have UI and for it to be good is a key factor of a game of any magnitude, he has already done a extremely good job the way there are now but what I had envisioned was something like extra windows for things you can place over the screen, not just have it fixed at the bottom..Example have an extra window for the poisons menu which you can get health from and don't just need to click F1, move mouse at bottom right corner click health poison click F5 keep playing....it really annoyed me how it was set up...but its his project and I dont say I know ANYTHING about anything related to this project but if its possible then he can at least look at the possibilities that kind of system can bring...this isnt me telling him what to do and i don't want it to be presented in that view but it would help( Just my 2 cents (as they say))
i don't know what limitations the game gives you but if its possible then I think it would be a great mechanic in the game but I understand if you cant edit the User interface.