Yes, I see what you are saying regarding other high speed types, but would any of the piston fighters available for conversion/development have had sufficient speed in the climb to get to the Mossies in time? Wasn't this a perpetual thorn in the Luftwaffes side throughout the Mosquito's wartime career?
I don't doubt that they had aircraft equal to or even slightly ahead of the Mossies performance by 1944. But was the margin enough to effect an interception of a high flying high speed threat?
I suppose much would depend on warning times.