I would ask your touchscreen-disabling-preference question on this
PRS+ thread.
PRS+ is custom firmware which is actively developed by the person who started said thread. It might have the feature you want or the developer might be interested in adding it. If the feature hasn't been added, someone on that thread will let you know. If it can't be added or is too impractical to implement, the dev will probably tell you.
I haven't gotten around to using PRS+ yet or I'd have been able to tell you myself.