Gonna tuck everything into one topic, so I will get everything written down.
Issues:
I have had issues where a person being sucked into a belly before the person's next turn crashes the game.

When positioned right, the enemy can be sent into an endless, inescapable loop of attacking your unit, ignoring the enemy blocking the path to them, shooting them even well after their death, forever. Never deciding to eat the person blocking the path, and shooting the unconscious body over and over again.

Suggestions:
A person with the means to remove or having the traits of spitting up what she was forced to eat. 
A growth mechanic. Either a spell or an effect, such as a slime or effect on a boss or a potion effect, which during the duration, eating enough enemies will grow their size, which could have effects such increasing sprite size, increasing movements and even attack ranges, and the like. And if possible, occupy more squares.  You can control how fast or even caps of sizes by scaling up how many digests before moving up stages, on top of level. Could make interesting boss fights, particularly the lamia queen one. Seeing her not just levels but just scale increase the longer the battle goes on. And of course, effects end or for a slime, they just divide down, basically creating more of an army periodically if let grown to certain sizes. 

Evolutions. I love to see the lamia queen have a unique sprite for sure, but I love some kinda evolving the vessels mechanic, I am imaging this upgrades skills, upgrades passives and abilities, gets new flavor text in a section, and a new costume.I like to imagine that you gotta feed them to bond level, fuse enough of the same type into them, and lastly do a quest to unlock the evolve material for them. For lamia it could be helping them reach queen dom, for the brunch squad, it could be varied. heck, for Sampo, you could have branching evolutions, one that could make her accept being the best prey there is, boosting her ability to haul back other prey to a pred on your side...or you can transform her into her own pred if you encourage her ego. You will always have multiple sampo, so you can get a few of each type. 

Butt growth. Enough Said. Heck if I could get a front and back view of the chars, especially the ones with AV, I would love that. Just a little button or even in costumes that just gives you a sprite with their back facing you. (Also thiccer gobbos :3)
Absorption: Just someone who you can sink into the curves of, and a chance of being pulled in when you strike their form. Evolved Absorption can even temporarily steal (approved) traits, and levels of their prey.

Conversion: This might be tricky, but I'd LOVE with someone like the goblin, to, similar to the summon mechanic being mentioned, she has the choice, soulgorge, to empower herself, or pamper specifically a corrupted enemy, and it could turn them into a gobbo or gobified summon. 
Some fun thoughts. Also maybe like transformation esk abilities that can temporarily turn characters into a different char. (Also seeing gobififed versions of the other characters could be silly.)

AOE Vore: May have harsh requirements, but seeing some evolved abilities having a splash zone, be great. (Same for Schordinger's potions as it evolves.)

Expedition/Quick/World/Patrol Battles: A thing off the main quest, and such, but this is could be a fun mechanic where you have slight randomized battles in the world, where you send a patrol squad out, get some resource. Thing is, you can be visited by enemies you defeated before, or get recurring enemies, ones who retreated or won before, who maintain their levels, maybe even evolved since ya saw them (or grew, for the few enemies that do). Beat them, could maybe get a free amped up recruit, or a larger reward if you feed them a few times some chaff before beating them. Just something silly to think on.

These are just the few initial thoughts and concerns and ideas I had while playing.