So, if you could give any one character Affinity, allowing them to be in 1 other faction (thematically probable or not), who would it be and how would you build with them?

Mine would be giving Mace Windu, Legacy of the Light Side affinity for Mandalorians. These squads reek of NPE, but they look fun:

--This Party's Over... Mando Style--
65 Mace Windu, Legacy of the Light Side
28 Kelborn
56 Neo-Crusader Officer x2
24 Mandalorian Tactician
6 Mandalorian Demolitionist
9 Mouse Droid x3
12 Ugnaught Demolitionist x4

(200pts. 13 activations)

The usual Kelborn/Neo-Officer setup. Resol'nare out and cannon the life out of whatever is unfortunate enough to be near Critdu. Probably cannon Critdu first, then move him up to another target (even if he needs to spend FP, or sacrifice his attacks on his own turn), and then cannon him again.

Easy to Copy/Paste version:
--Mace Windu the Vindicated--
65 Mace Windu, Legacy of the Light Side
58 Mandalore the Vindicated
28 Kelborn
23 Mandalorian Captain
5 Salacious Crumb
9 Mouse Droid x3
12 Ugnaught Demolitionist x4

(200pts. 12 activations)

With Triple/Twin/Ruthless, Kelborn, and FP to move faster, Mace can essentially move up to 16 squares can vaporize a big piece. Damage ceiling would probably be about 200 at least, maybe 280, since he's likely to get at least 1 or 2 crits with 12 attacks. If you go up against a swarm squad... good luck :P

This one is actually fairly realistic but I would make Pong Krell have affinity for seps. Uber reserves team yes please. Too fulfill this fantasy I would also make that affinity replace his rival other wise you wouldn't be able to get the reserves one 1 roll.

--The House Always Wins--
61 Pong Krell
57 Count Dooku, Separatist Leader
43 Wat Tambor, Techno Union Foreman
15 Lobot, Computer Liaison Officer
12 Gha Nakt
10 San Hill

198 points
Now that is a reserves team, reserves on 1, 5, 10, 11, 15, and 20. Varying from 20 points to 70 points each turn.