This is the exact strategy Microsoft used for lock in way back when. You could use ASP and other MS technologies and they even worked well. Until you wanted to exit their walled garden - then they were a real pain to integrate with anything usual.
Isn't AMP available as an open-source library? I don't see the lock-in.
Besides, Google has announced that search rankings will be affected by speed, not by what library you use. So, if your site is already optimal (doesn't benefit from AMP) or you want to use some competing project that also does a great job, you won't be penalised.
