Ultra Magnus - silver bumper, white gun, blue in place of red on the trailer for better 'bot-mode accuracy and overall more cohesive look.
And since they're doing that Evangelion crossover anyway, let's see UM in Eva Unit 00 colours.

Bumblebee - Glyph repaint, using the alternate facemask. Also Goldbug, and pretty much any other character they could squeeze out from it. I'd pick up a Glyph, and maybe a Goldbug.
And a separate Spike release, under the Legends line. Maybe as a Deluxe-price set with Ratbat.

Barricade from Prowl would be cool.

MP Cassette redecos - MP Enemy, MP Garboil, MP Wingthing, MP Howlback.

MP-11 into MP Action Master Skywarp. Why not?