With the godsend that is the fuel cell system, comes the jarring transition of the inflexibility of how the empty cells respond to liquids. In many cases, these cells could be used in such a way to farm masses pools of lava or water instantly on site...
The problem comes when the site is either completely tapped out, or completely full of flowing liquid with the source blocks partially inaccessible to the player. The clear solution to this is to use Buildcraft Pumps for their AoE collection of the Source liquid blocks, but then the liquids are 'trapped' into BC tanks that cannot be accessed by empty cells. For lava, this is a minor annoyance, as BC integration with Geopower is part of IC's base, and flowing water can be put into cells via the IC Pump...
Yet in the case of Nether energy production, there comes a difficulty in how to send lava back and forth between the Overworld and the Nether. Sure, you can use Ender Chests and deposit your cells in them as you fill them next to a Nether ocean, but you still can't access all the lava without tremendous effort. You could pump the lava with BC Pumps, but how are you going to send that lava to the surface with resorting to RE Batteries or Lapotrons?
So what I suggest is the ability to right click on BC tanks to fill cells with its appropriated liquids. This function used to exist with an add-on called the Mobile Pump , and was a highly useful tool at the time. I'd like to see something similar with cells to come back for the simple function of pulling directly from BC tanks...
And on a side note, any chance for Bio Cell <-> Biomass conversion if this were to become implemented?