I am strongly of the opinion that WotC never intended Fringe characters to change faction via Affinity.
1) Over 16 sets, they avoided the situation ever coming up. I don't believe that was merely coincidence.
2) The rule book and glossary never describe Fringe as a "faction".
Quote:factions
These broad categories classify characters according to their allegiances in a particular Star Wars era.
Quote:Fringe Squads
(play option) Instead of playing Light Side against Dark Side, with the occasional Fringe character thrown in, you can create a Fringe-only squad. Such a squad can’t have any characters from other factions in it.
Quote:Faction: Your squad belongs to a specific faction, which corresponds to the sides participating in the
battles that rage across the eras. Factions have an affinity for the light side or dark side of the Force and
are described on page 15.
Each character’s stat card has a symbol that identifies which faction it can fight for. Characters with the
Fringe symbol can fight for any faction and so can be added to any squad.
If you take the wording of Affinity at face value, it would seem that a Fringe character would change faction. That said,
in my opinion the wording didn't take Fringe into consideration because Rob never intended for it to happen.
This is an arguable point, of course, but I think it makes sense.