God I love monster hunter and this story for ideas I just have an anti idea no summoning only eggs and even then super rarely don't get too many too alot of fanfics have fallen to variants of this trap. Also don't be afraid to make your own version of sub species and such give demon doggo some love don't forget about him.
During this fanfic I've been wondering for a while now did you forget or didn't know about Ryuko Tatsuma she can turn into a literal dragon she is a number 10 pro hero why is everyone freaking out because he can turn into monsters. We got lizard people and Giants as well.
This was a really good story, I really loved it, in fact it's what made me start reading fan fiction. I don't even know if you're still active on this platform due to you're last "interaction" being 2 months ago but if you are still active, please either update or tell us that the story is dropped.
I love the story and the design of his power however you're not doing yourself any favors by designing him to seemingly continually collect more monster of wich a majority are obviously gonna be "trash". Maybe design some kind of cap on his monster pool to force him to focus more on developing what he has rather than acquiring now ones. I would love to see him focus on strengthening his current forms like his defensive aquatic monsters and essentially creating different setups and strengthening those. Having said all that great job on the story so far.
DimensionalFish