Solar, I don't mind you having an opinion, but I do take issue when you post assumptions as fact.
If blocks do get full, InstantX transactions will start to be unlocked.
100% completely and utterly false. IX locks are mempool entries same as transactions. They don't get flushed until the transaction gets written into a block, regardless of how many blocks that takes.
And, your disappointment is simply impatience. The very last sentence of the proposal states:
If approved, a proper development, testing and deployment process would start before it reaches production. Let’s give Dash room to grow.
The process is already happening, there's just no need to implement it anytime soon.