I was lurking around, and then I found this, so I joined.
As far as Blanka Ball goes, the idea you have now, to use the Screw attack seems like the best choice. As well as Kyzon's suggestion for the electricity, as that was what I was thinking. Here are some suggestions I have for move placement.
D-Tilt could be Blanka's slide attack in SF4, and his D-Smash should be the sweep. The sweep could possibly be edited to be more like Mario's D-Smash.
Standing fierce Punch can be the F-Smash, with the charge up being at the point where Blanka's claws are at their highest. This attack in SF4 becomes an anti-air when when the foe is jumping so, I'm thinking to use the AA version as the Up Smash too.
Crouching fierce punch could be the D-Tilt. While Jumping fierce punch could be the F-Air, possibly with a range buff.
Jumping roundhouse should be the D-Air, and Jumping Medium Kick could be the N-Air.
U-Tilt could be Standing roundhouse, however this could also pass off as a U-Smash.
Rainbow Roll is a Perfect Up-B, but as far as his ball attacks go, I'm guessing you could use Electricity as the Neutral-B, with his normal Ball as the Forward-B, and The Ball Super (Where he rolls around on the ground), as the Down-B. Or you could switch Electricity and The Ball Super around.
As I said, I'm not sure how PSA creation works, do you have to use Animations from DK? or can you take animations from other characters and modify them for DK?
My friend, I've been waiting for a response like this =D
First off, the only animations I can use are the ones DK already has programmed in. So no go for the sweep.
Screw Attack Blanka Ball is a given. His shaking IS a good idea, so that's settled. What attack should I map it to? I wanna be smart in what I map to the B moves, because they are the only moves that can leave the ground, and I don't want to waste them.
Using a momentum code I can make DK slide forward, but do you know of any good animations that would look like's Blanka's?I don't know any 0_o
Rainbow Roll was what I was thinking of for the Down-B, but Up-B makes more sense =P I was also thinking that tapping B again would make him drop straight down...what do you think?
Fierce Punch is iffy, 'cuz I dunno of any good animations. any suggestions?
Basically, the biggest problems with your suggestions are animations. But awesome ideas though, I need more people like you

Good idea for Rainbow roll, but why not expand on it, when Blanka preforms Rainbow Roll EX he can change the Roll's trajectory. So how about by Pressing B, and then a Direction on the D-Stick, you can adjust the Roll's trajectory in that Direction, (Example: By pressing B-Down you send it downwards, and by pressing B-Forward you send it more Horizontally, ect.). It seems like a really good representation of Rainbow Roll EX.
Specials Move Map (IMO)
B: Electricity (I don't know if this can work with the A combo being Electricity though)
B-Forward: Blanka Ball
B-Up: Rainbow Roll
B-Down: Super Roll
Final Smash: Electric Ball (SF4 Ultra)
That's just what I was thinking.
This may seem odd, but DK's downed Status animation my be workable into the Slide, with some momentum of course. I don't know about the Grounded Fierce Punch but, DK's U-Tilt is a really good representation of the AA Fierce Punch.
DK's D-Tilt, though iffy, could possibly make a good version of Crouching Fierce Punch. I don't have a clue for Jumping fierce punch.
Finally standing Roundhouse, while this is also really strange, could be DK's backwards jump, this animation would be PERFECT, if you could just get it on the ground.
Dk's Down Air, if you tilt it to the side, and then make DK drop continuously while using it, like with Sonic's D-Air, could be Jumbing Roundhouse.