Suggestions in DONTFORGET
Maybe have a Rainbow Monster SOUL as an option when unlocking the Rainbow SOUL itself after getting 999 of each GachaPog. So you feel as if you're playing as a Monster that absorbed all the Human SOULs (Purely cosmetic of course.)
@RickyG 
I have a bit of an idea. Maybe add partner trading to DFC, basically allowing people to trade partners, and it could be the first trading system in the game (because technically transferring money isn't trading).
Can you add a way to send the player back to the main menu? Asking this now especially because of the multiple save files, so if you feel like switching routes, you can do so without closing and reopening the game.
that they change the battle style of the pvp and put the one of deltarune, and that they put the nose at once,thanks
postscript, add lucario
Make a 2v2 type of battle system possibly, mostly using the Deltarune battle system as well.
Being able to edit artwork would be nice, since if you wanna add onto your artwork you have to completely restart.
Something that would be REALLY appreciate, is the guarantee of fleeing 100% of the time against an enemy you befriended with, if you're on the genocide path, it's not a problem but if you're a pacifist and don't have access to the Pacikiss... torture
Heres my idea for costumes
Drip temmie: to get this costume, Unlock tem armor, costume is to: deltarune temmie
Golden chara: like gold frisk but chara
And lastly a character
Mrs. Toriel: Deltarune character
Magic: Fire
Description: Goat Mama But Teacher..
Because you can meet multiple enemies, this greatly reduces the efficiency of brushing monsters, so I hope I can turn him on or off in the settings.
random cool idea, the doggos, like Lesser and Greater Dog as vessels. They'd both be either Normal or Fighting in terms of pvp magic, and would be quite fun