Im torn ....
Possible driver mod or mod host to XM-L
Could this be the AA - 14500 , I have been looking for ? [ So far none of the ones I have are perfect ]
So which one would you be interested in ?
That 16340 looks pretty nice, especially the button for the switch.
Would you say that in general the hosts for xp-g lights like the Trustfire A3 are better made than for xre/xpe light? Most of the cheapo lights I have seem ill suited for 3A+ operation. Often the springs in the tail aren't even soldered and depend on pressure to keep contact.
The J10 looks interesting. Why is it that everytime I click on a thread around here the result is that I have to put 10 or 20 bucks more into my PP account?
I would choose the J10 because it looks very cool to me and also because of it's smaller size. I have a lot of bigger and brighter lights but the ones that gets used the most are the smaller more compact flashlights. 
Spending other peoples money.
I'd go for the M2.
Why? I hear you ask.
Well I've got a weakness for good little AA lights (amongst other things).....and I'm a sucker for XPG's.
Which battery would work best with an XML, a 14500 or a 16340?
In theory the 14500 should be better , but it comes down to cell quality ...
Light quality = ? Highly variable , I dont think the emitter makes a whole lot of difference to the quality of the light .
But so far I would say XP-E XP-G emitters are found in slightly higher quality lights than XR-E
3A , Yeah , not really the sort of thing smaller lights are built for , but experimenting is fun ...
I have a 14500 AA XM-L [ Trusfire F20 ] , and a RCR123A XM-L [ Ultrafire A20 ] ...
The Ultrafire M2 is tempting ... + I have a bunch of RCR123A EDC light already , and they all work as they should .. Cant say the same for the 14500-AA though [ search continues ]
The best little mod host bar none , is / was the Ultrafire A20 .
I had to buy the M2 , as Im still seeking a decent AA-14500 flashlight ... [ budget ]
My jetbeam is a fantastic AA , but no support for 14500 ... [ At least I dont think so ] and its not really budget .
I'd go for J10 (with a emitter swap). M2 is really good, also because it use a XPG, but is another "akoray" replica.
Its made the to buy list , but not just now . Maybe June .