The team-up between Dregg, Shredder and Krang should have been the finale, it tied up virtually every loose end, even Carter. Had the last part of that arc ended with Splinter telling the Turtles they had ‘graduated’ then it would have been perfect.
So that’s just what I did. Took the last scene of the actual series finale “Divide and Conquer” and integrated it into the episode “Turtles To The Second Power” to serve as a more fitting conclusion to the original series.
Also, the actual final scene of “Turtles to the Second Power” annoyed me, it doesn’t end on a punch line or something from the Turtles, the last word goes to Carer, he is transported to the future and then it just abruptly ends, so the new ending I find adds a lot more closure to things.