After incorporating a number of suggestions from you, there is now a semi-official archive of compatible addons for TenFourFox. This is not to say only these addons are supported; it's just to make convenient finding ones of significance that do work. If you have other recommendations, please advise. I'm still studying the right way to directly install from this folder without opening up a security hole.
Watch for the 45.9 beta in about two or three weeks.