I think the author is getting stuck in tactics, not strategy.

Problem: OP does not have the freedom to pursue what he finds interesting.

Tactic: Given existing work arrangements, attempt to negotiate a setup where he can just work on what he wants. If the employer changes its mind, OP gets to restart the cycle.

Strategy: Avoid having this problem in the first place.

Pursuing the strategy means taking a high-paying job, saving a large fraction (https://www.mrmoneymustache.com/2012/01/13/the-shockingly-si...) and having the financial freedom to never worry about this problem again.