Yeah, I don't think it works for copyrights, but patents already seem to have this solved. There's already a set unit for them, and they already cost a substantial amount of money (unlike copyright, which is currently free).

Keeping things secret now to patent them later is a problem, but no worse than it is now, I think. The same incentives apply to the exponential scheme as to the current hard limit. You'd keep the requirement to file within a certain time of the first public reveal, so you'd have to move quickly if you wanted to patent anything you were actually going to use.