Suggestions in DONTFORGET
In the settings menu while in game (cell phone) add an option to leave to the main menu, like if someone wants to switch from offline to multiplayer or the other way, or switch files in any of the modes they dont have to turn the game off and on :D
Replace the PVP Log button in the Cell Menu with the Dimensional Box, allowing for access to Box A and B like in the original UT. The PVP Log itself should be moved to the actual PVP menu.
Made a couple of mock-ups on how it all could look.
Can you put this time proper text for acting with the characters with the P-Action?? Like with Niko, he say with his p-action in froggit.
"Um... You are THE frog."
Or Ralsei says:
"Can we play to jump later if you want!"
Get it? 
Abillity to reset your SPARE/Kill count.
The same spot where the credits are in the Last Corridor you'll be able to reset your spare and kill count. Here's the catch
for example: your kill count has to be above your spare count exp:
100 kills < 30 spares
The implementation of Undertale Yellow both on the map and in Vessels, or bosses just like they did now in 2.7.9
It would be interesting to see Clover, Marlet and Starlo fight Ceroba in a 3 on 1
Dear developers, please make this attack a little easier. It is difficult for me and probably most beginners to dodge it. Thinking you understand why.
(It is especially difficult for pacifists)
you could add a warning system so that people that did something wrong would be warned(for example 3 time and then banned, that would make it easier for people that want to redeem themselves to enjoy this amazing game
this is just my personal opinion but I think it'd be better if you added a way for banned people to join online servers whether that would be together or just normal people that would make it more enjoyable for everybody
There's only 3 flowey expressions, why not add more?
It's been said before but there's still time, more expressive animated sprites hell just make em move a bit instead of being still, oh and maybe make them colored, or pull a Tsunderswap and just give em flavor