I wasn't really playing much before the DOff system was launched, but I do recall reading somewhere about them doing something with the Bridge Officers people already had from the Diplomacy system. I never found out what though, and completely forgot about it, until I saw someone talking about their Veteran BOffs, which reminded me.
Did anything happen to existing BOffs people had from Diplomacy? Were they traded in for rarer versions, or something like that?
Originally, people who leveled the pre-doff diplomacy system all the way got the Federation Ambassador title, transwarps, a dress uniform, and an enemy faction bridge officer, just like they do now. However, those boffs were originally "common" (white) quality.
When the doff system went in and diplomacy was folded into the new commendation system, those common enemy faction boffs were removed from Sugihara's boff store and replaced with purple boffs.
Folks who already had one of the original common diplo boffs kept it unchanged, and were able to choose one of the newer, higher quality boffs, too.
Those who hit diplo 4 after the change only have access to a single purple boff, so in effect, "early adopters" of the Ambassador rank were rewarded with a second boff.
The "Veteran" boffs were a reward for people who lost out in the great currency conversion.