Is there any way for me to sign extensions myself and trust my own root? I trust Mozilla about as far as I can throw them. How long until they withhold their s

Is there any way for me to sign extensions myself and trust my own root? I trust Mozilla about as far as I can throw them. How long until they withhold their signature from an extension which blocks ads from one of their funders, or which supports a political cause they dislike, or are pressured to dislike? In fact, what assurance at all does Mozilla's signature give me? As far as I can tell, none whatsoever.