S! all
As someone mentioned above, the Me163 got only 9 kills in all the time it was operational. That is with 2 Staffels flying it starting in mid 1944. Far more than 9 German pilots crashed, got dissolved, exploded in mid air or were shot down. The Me163 was a failed experiment, continued only because Hitler liked the idea. If AH creates a fictional functional Me163 that is not subject to the problems, then perhaps it might become popular. But if the flying pilot has to deal with the real German pilot's possibilities of dying, then I doubt many will want to take the chance.
Build a Me163 when you've got nothing else left to build. (and include a sound effect where the pilot starts screaming when the C-Stoff or T-Stoff gets on him and starts to dissolve his face) Right now a 262 is a far better choice for investing the limited HTC development time.