Well, I tried and made such a version, but I’d label it “beta” for now. Having more elements to interact with, makes things considerably slower. On my PC here the performance is somewhat sluggish. Check it out on http://renoise.hit.bg/beta/ and let me know if it works reasonably.
There are page buttons above the position and velocity sections: 0-63 and 64-127. Having all the positions on one page would make the sliders too thin to control.
It’s hardcoded to 128 rows now. I can imagine 256 will be unbearable. OTOH, making the row count dynamic may help for the general case of 64, but it’ll be quite complex to do. I’m not sure it will be worth the work. You could always generate several times for longer patterns.