Things that I'll suggest:
1.) There should be some type of small multiplier or bonus based on streak length.
2.) If you're releasing new coin shop items periodically, as you should, try to have more variety. A lot of females spar, so feminine options would be nice.
3.) To promote sparring long term, I still think you guys should re-release the old milestone hats (and/or add more). These should be a thing all the way up to 100k, maybe at the intervals of 1k, 5k, 10k, 25k, 50k, and 100k. Players were never told that those hats would be exclusive, and I think they should be brought back so that there are long-term goals. This has received overwhelming support: https://www.graalians.com/forums/showthread.php?t=23696
At bare minimum, bring back the hats from old at the same milestones as old. Doing this would create incentivize for a very long time with very little work required.