Most features are 'possible' to implement. How soon they are implemented comes down to whether you are wanting to pay for my (or another developer's) time to implement them, or whether you want to open an issue on tracker.moodle.org and wait until I (or someone else) has a bit of spare time to work on it.
In this instance, there is also a question of how the limitations would be applied - would you want to define a new limited role that was only allowed to book a certain number of hours / individual bookings (with the limitations in question being set on the global settings page) or would you want to apply those same limitations to all (non-admin?) bookers? The actual code for the limitation would be fairly simple, it is the extra settings / capabilities / etc. which add to the time taken.