Perhaps the floor or limit should be based on a percentage of your last finished games. The percentage may need to be adjusted for the total number of games also.
And to throw in another idea to chew on.
What if rated games had to be played with someone within 400 points of your own rating? All other games would be automatic non-rated. That would help smooth out rating jumps and encourage players of wide ratings to play each other without worrying about hurting their own ratings.
* Have a ratings floor based on a sliding percentage of your most recent finished games.
* Your rating could not drop below the floor due to timeout loses, but could for loses by check-mates and resignations.
* Have a maximum player rating difference for a game to be rated.