LavaGenerators can be filled with FluidPipes, (the act as FluidTanks) so to slove that.
Generator can be filled with fuel only from the Side. I hope that helps.
(Also Putting in a Stack of lava Cells into a Geo Gen last a really long time so no implementation)
Had not tried filling generators from the sides as its normally top/bottom but that seems to work, and i'll be able to work with that, thanks!