How about :
Prologue - Young Hank and Janet vs Winter Soldier
Eric O'Grady steals the suit (Ant-man III geddit?)
Early 60's marvel monster tribute as microscopic lifeforms are enlarged to giant size, start evolving rapidly and given nicknames like Moomba and XEmnu etc. and cause chaos in S.F
Tween Cassie Lang ends up using suit.
After-credits : Bill Foster and his Nephew take a trip to nearby Oakland and go to the Wakandan centre...