You don't need a harvester or something because it's soooo easy and fast to get biofuel and the biomass is just starting technology.
Just harvest a few time, fill up 2 storage containers with leaves and wood and use the constructor to assemble biomass and "eu vola" automation .... or half of it.
After that, you can use the merger to merge two belts into one to feed another constructor to craft biofuel.
I have 2 Container full of biofuel so idc about "harvesting". Ok have to do this a few times but it takes just 10-15min to have a full container again.
Anyway in the late game, there is the coal generator with 50mw and to be honest after that, you do not need the biomass burner ever again.
So no i dont think we need a "harvester" it would make the game "to easy"