You're right the kernel might be able to handle that pretty quickly, but I know from experience even good, ~200Hz sampling captouch system is 1/200 = 5ms worst

You're right the kernel might be able to handle that pretty quickly, but I know from experience even good, ~200Hz sampling captouch system is 1/200 = 5ms worst case, 2.5ms avg. That's already 2.5-5x the budget and we haven't gotten off the display.