Lately, I've been able to do a full re-watch of BTAS, Batman Beyond, JL, and JLU thanks to HBO Max. After going through all of these series, I started to wonder what could happen in the BTAS sequel that is reported to be in the making. JL & JLU opens up possibilities for team-up episodes, while Batman Beyond restrains what be done w/ the bat family.
Can do:
Team-ups w/ any league member (JLI teammates, brave and bold, etc)
Static Cameo
Material from the BTAS Comics (most notably, the barbara/dick/bruce baby situation)
Bruce and Barbara
Tim's Teen Titans
Additional Batman villains (The court of owls)
Royal Flush Gang
What led to Ra's's death
Life after joker was killed.
Batman Inc. (Katana, Metamorpho)
Renee becomes the Question
Can't do:
(Unless they make Beyond non-canon, many of the Can'ts are solely due to this series)
Damian Wayne
Additional Robins
Bruce having a lasting relationship (Selina, Barbara, Diana etc.)
Would love to hear any additions to this list.