Okay, so this is less of a me thing and more something Robby wanted to try to give players more places to farm monsters. From what I can tell, here are some places I think would be cool for an expansion.:
Gas Station (Area 10): This mountain can be climbed on top of in order to allow players to fight against more Shagdaws and Hellshags and potentially some Spiked Squishers: http://prntscr.com/12m5ubs
Factory Passage (Area 24): A climbable version of this mountain where we can fight more Armed Dillos would be nice (plus it would fix a few issues): http://prntscr.com/12m6f3x
Sewers (Area 26): This part of the map could lead to another sewer area that can allow players to ride Dumtilians out of the sewers: http://prntscr.com/12m69bf
Don't be surprised if you see me wanting to change up the Dumtilian's Eliapedia entry to reflect this change, though.
Red Leaf Hills (Area 32): This area can be expanded both southwards and eastwards to show off the land's river: http://prntscr.com/12m6l36 (River in Area 33: http://prntscr.com/12m6np7 ; River in Area 7: http://prntscr.com/12m6p5u)
Renegade Yard (Area 35): The entire field south of where I'm at here can be turned into a field for farming Logons: http://prntscr.com/12m6t9u
Red Leaf Hills Lookout (Area 37): More upper level of the mountain, dammit: http://prntscr.com/12m6xg6
Cave Entrance (Area 38): The only expansion I think it would need is to widen this dang narrow passage: http://prntscr.com/12m70sf
Scorpee Territory (Area 48): I think this entire south area should be given more credit: http://prntscr.com/12m7n7n
Great Frog Territory (Area 58): Maybe these mountains can be expanded on, with Scorpees roaming them?: http://prntscr.com/12m7vnu
Also, this part can be expanded northward so the froggies can actually move around there: http://prntscr.com/12m7xk3
So yeah, there's that.