Just leave everything the way it is. You can not compare ratings across different systems, don't try to do it, it will never be perfect. Ratings are designed to compare players in the same system. So I don't see a problem with growing bullet rating. 2100 in bullet here will beat 1900 60-70% of the time, despite the fact that in reality the could have 1800 and 1600 OTB ratings respectively. The pools of players are really different in OTB and online systems.
Second reason the rating scale for bullet is really distorted. On popular sites like ICC and Playchess some GM players have bullet rating of 3600! Other GMs have 2600 (1000 points less). In reality their FIDE/USCF ratings could differ by only 200 points. First, reason for it. Is that bullet is not real chess. It is hard to compare to OTB because the bullet rating is influenced by completely different factors such as speed of thought, knowledge of offbeat/tricky openings, etc. These factors might not be that important in OTB chess.
Second reason, most top players on these sites play only other 3000+ players, thus they essentially create a subpool of players inside of a larger pool. This makes the rating scale distorted from 2500 - 3600 rating.
It's funny to see how chess.com admins try to match uscf/fide ratings with bullet. It can't be done!
Ratings are not comparable in time or between styles. Time inflates ratings as they tend to be lognormalish - so new players get and averagish rating which contributes to the "pool" of ratings. Players leave behind bad ratings but re-enter at average and keep good ones inflated. Maybe when a player leaves the pool, or doesnt play for a time, you can remove their entire effect from the ratings by marginally degrading all of the players?