Here is a very simple idea: Play rhythm changes on the piano every day, blind-folded, for a year. The blind-folded part is probably the least important. The idea is to increase one's proprioception, that nice little sense that tells you where you fingers are without looking at the piano. I can play ok without looking, so that's the easy part.
I know the chords, so that's not particularly onerous. My weakness is in the improvisations, which sound very square to me, relying on a few cheap tricks. But I figure with a year, I can find some ideas.
The "year" and the "every day" part are what's difficult. Since I already play piano every day, I could do this, but I also want to play other things. And then, the experiment might fade in interest for me after a few weeks or months, rather than lasting a year.
Still, it is a good concept. The idea would be to change it up if it got boring, so you could do only bass line for a week, or do it in a weird key, or work on a particular song with rhythm changes as its basis.
[The chord changes to "I got Rhythm" by Gershwin is a standard vehicle for improvising in jazz, and for writing new tunes with the same changes, or variations thereof.]