Is there a way where I can enter a number of notes, without worrying about note length and rhythm, and then separately experiment with different rhythms? To create the happy accidents you would get on a 303.
I feel that this is really far from the current step mode workflow and would be really difficult to add to the Pyramid. What you can experiment with is a combination of transpose master track and eucllidean rhythms, which gives interesting happy accidents as well. But the actual TR-303 programming style is really unlikely to happen.