Input you require, input you shall get.
Ideally you will need a front dogone that is 72mm or shorter, more like 68-70mm since the UE diffs use an 8mm pinion shaft, which is longer and sticks out further than the stock emaxx type does. You have a few options, such as a custom made item from mike, or use the 3.3spec center ( perish the thought ), or have a dig around parts listings for various dogbons until you chance across one the right length....
The battery mounting idea seems fine, and i have seen several that use that idea for mounting either lipos, A123 bricks etc- just need to know the dimensions of the lipo you will use, make cardboard bummy battery and take it from there to design your mount.
the hex issue is a well known one, but thankfully I think DACE or someone similar has produced some adaptors specifically for those type of CVDS... only trouble is I cant remember the trhread they were mentioned in!
You could however easily just use something like
THIS for 14 > 23mm. I have also seen 14 > 17mm adaptors that just sit ontop of the 14mm hex... again I cant remember where though but as always googling should turn up the answer.