How about swapping in @kku’s Filter+ gramplet variation for 5.3 and inviting people to do some testing with a few sample Trees? The project could gather some statistics from a wide variety of hardware configurations.
Also perhaps you could add a Cache scaling preference?
So users could dynamically have Gramps incrementally scale when record count exceeds a certain base number?
We have a LOT of filter rule requests in MantisBT listed in another thread.. They could be a good project for the community to work on as experiments for boosting Query performance.