In case of demanding fleet basing right in a peace deal: I wouldn't have to pay for this fb right? At least for the duration of truce (if it's not automatically canceled after this). Also, would a military access and fbr obtained in this way boost relations?
I would think the best implementation for enforced fleet basing rights, military access, or transferred trade power would be either:
a.) The length of the agreement is specified and modifiable in the peace treaty, and not just an automatic 5 years for the truce period.
b.) Have the effects be permanent but once the truce period ends the defeated party gains a CB against the conquering party to throw off the effects, much like an independence movement.
I think (B) would be ideal, but (A) would be much easier to implement. Heck, speaking of modifiable lengths-of-contract it would be really interesting if the truce period could be negotiated and not automatically 5 years no matter what. A conquered nation could negotiate for a longer truce by giving up more territory, or vice-versa.