You can do ex power up after NJP and still combo afterwards with f4 xx ex bladeslice - run cancel - b1,2,1 xx kanoball for 44% dmg. Not sure if you can get something more damaging by run cancelling after ex powerup as the timing is kinda strict.
Maybe ex buff could have applications mid combo after NJP? Gotta do some testing.
Edit: Not enough time to do anything, even a raw ex bladeslice into NJP into ex power up and still combo... buuut here is a corner combo after NJP:
NJP - b3,1,2 - 1,1,2 xx ex bladeslice - 1,1,2 xx kanoball. 55% for 2 bars.
Good find! It's weird but you can hit NJP, EXBuff, F212 midscreen for some good damage
I noitced in the corner you could do 112 xx BF3EXCancel, NJP, DD3EX, B312, 112 xx DB1EX, 112 xx BF3 but all that comes out to 54% with 3 meters so it's actually worst lmao, gotta love EXBall scaling. Sadly I couldn't find a way to get more damage than your corner one
Any Midscreen: NJP, DD3EX, F212, MicroRun xx 112 xx DB1EX, Run xx B12 xx BF3 (50%)
Near a Wall: NJP, DD3EX, F212, MicroRun xx 112 xx DB1EX, 112 xx BF3 (51%)
Corner: Same as the one Smoke posted (55%)