Almost everything with good performance on the C64 is "weird" or "custom" in some way, so I don't think you need to be too afraid. In fact, Shallan is making a D81/floppy fast-load framework that works without the C65's ROM, precisely so that he can use all 384KB RAM. This would probably also solve your need, and you can then use something that someone else is maintaining, and thus make your life and conscience easier 
LG
Paul.
