The one thing that I will add is again one of form and function....
The GG Grant @ 20mm diameter, in my opinion has the perfect form for function ratio. Add another 3mm and the form starts to take a hit in favour of function. Now while 3mm isn't a huge amount bigger, the diameter will of course be a little bigger.
So there will be the people who absolutely love the multi purpose full functionality of the GG Transformer, but there will also be those (like Fred) who prefer the sleeker simplicity of the 1 piece GG Grant which still has both form and function in abundance.
For me the only real advantage of the Transformer over the Grant is the 18650 battery which provides the best runtime @ 3.7V.... however, I rarely use 3.7V so is this really an advantage, and when I need 3.7V, the AA size 900mah battery is more than satisfactory.
So my opinion (which I have already said in private), is that you have the Transformer to satisfy full functionality, but you keep other models because not everyone will be satisfied by functionality alone. Of course you can't please all the people all the time, but there is compromise.....
OR:
If you only want to produce 1 GG = Transformer, which makes a lot of sense and is completely understandable, then you know my opinion on this, which is to only increase the diameter to 21.5mm (instead of 23mm). Then you have closer form/function ratio - the biggest 3.7V battery would be 1800mah + and most of the batteries would fit better because the internal diameter would be tighter = 17mm.
So the big question is would people be satisfied with a 3.7V battery that has a little less runtime than the 18650 (standard 18650 is 2400mah vs 1800mah) in favour of a better form (21.5mm vs 23mm) and generally tighter fitting batteries overall?
And remember 1800mah is still double the runtime of the current Grant 3.7V so far more than ample!
Anyway, that's my 2 cents...