Two points, the motor is smaller than the engine, leaving room, and weight needs to be placed well in a trike.I think the gas filler tube would be where I'd want to put the plug-in for the charge station (assuming we don't want to rebuild any of the body panels to incorperate an alternate hatch for the charger). My Leaf has a little hatch on the nose that pops up to reveal the charge port, and I really like the nose better than the side for this, but the starboard side wouldn't be bad.
As to what to do with the bulge, I think that could be used for incorperating some of the heavy gauge wiring for linking the batteries in the "gas tank" with the batteries and BMS under the hood. That way you don't need to re-wire the actual interior of the car too much.
So some of those batteries need to go upfront and some where the gas tank was. Don't put any high and rearward like in the 'truck' or high in the passenger seat, (not that you would).