Changing the homepage is currently not possible in Firefox for android. Hopefully this feature will come to Android devices soon, but for now there is no ETA.

I understand that limiting this to Top Sites has allowed FF to start up dramatically faster (and I sure do notice this). If only I could rearrange and pin sites for my 'top sites' list, and perhaps choose a couple of bookmarks to include, I wouldn't mind. That would be the best of both worlds, customizable and fast.

Having a bookmark on the android device homescreen is fine, but when I pop open a new tab from within the browser, I want my homescreen there too and I can't have it.

And finally I guess a lot of people would just outright like to see their own homescreen back again, perhaps give them the option along with some dialog about slower startup times? Stick it in advanced or even about:config if you don't want Joe Public to use it.