Also please allow to summon multiple creatures and not just 1 per character (saying this based on DOS History)
For this I will be quite interested to see how Larian are going to handle the higher level summoning spells. All are concentration spells, meaning you can't use them multiple times to summon multiple creatures (well for certain spells you can but it would be...bad - Summon Greater/Lesser Demon I'm looking at you). However, some offer variable summoning options that scale by spell level used, which would allow multiple summonings. What would be interesting for these is that, explicitly by RAW, the DM gets to choose exactly what you summon when you use the spell. I'd be interested to see if Larian stick to the rules on this and make the summoned creatures semi-random.