I think that there should be an increase in amount of babies/towers you can use to at least 6. For me the game feels too simple as there is very little different synergies you can do when you're limited to just 4. Especially when 2 of those slots are usually gonna be taken up by little chad and a defensive thing like cube of meat that just leaves you with 2 slots for damage/support where the real fun is. One synergy that I found really cool was how Pegasus can shoot out the fire of Paschal Candle and Freezer Baby's ice tear melts when shooting through it. Having to think about the ups and downs with certain decisions is what makes a game like Isaac fun. Maybe it is just me but with Isaac I think of having many different synergies with different things you get along the run and being limited to so few towers makes me feel like there's not much you can do.