So my suggestion is quite easy:
Instead of always start with bronze make it so that games with less arenas always start with highest possible low-league.
So in case of just 2 leagues make it:
Platinum -> Elite (instead of Bronze -> Elite)
3 Leagues:
Golden -> Platinum -> Elite (instead of Bronze -> Silver -> Elite)
etc.
The advantage would be: you always know how far away your current league is from Elite.
(I'm not sure diamond league still exist, if so just sort it in)
Instead of always start with bronze make it so that games with less arenas always start with highest possible low-league.
So in case of just 2 leagues make it:
Platinum -> Elite (instead of Bronze -> Elite)
3 Leagues:
Golden -> Platinum -> Elite (instead of Bronze -> Silver -> Elite)
etc.
The advantage would be: you always know how far away your current league is from Elite.
(I'm not sure diamond league still exist, if so just sort it in)