What is the issue? More high output drivers would certainly make the situation easier. But I see several solutions. :)
With 6x18650 load on each cell will mostly be in the 5-10A range depending on what type of output you are going for. You can use high capacity NCR18650BD cells (without protection) in that range. If you want to have higher output, then get some higher discharge cells, or more cells.
What is wrong with a linear driver if you dont need properly regulated output?
What is wrong with some of the regulated taskled drivers if you dont need the absoulute max bragging numbers that the X60M will only maintain for a very short time. Several of the taskled drivers can still maintain higher continuous output compared to X60M. And for most lights, they can output enough "oomph" to heat up the lights quite fast.
Another ways is making one light as 3 separate lights. That way you have all the options you have with a single emitter light. Just as an example. 3x 18650 in series x3 (not in parallel with eachother since that could mess up how the drivers works) 3x HX1175B drivers (with attiny 13A master for momentary switch) 3x MT-G2, 3x switches. Maybe one switch if that works and you dont want seperate control of the emitters (Seperate switches would be cool if you mixed MT-G2 tints though).
When that is said. 12 XM-L`s will outperform 3 MT-G2s in efficiency, lumen, throw, throw vs overall reflector size, driver circuit flexibility, CRI (depending on mix), tint (depending on what you are after and mix). The way I see it the only thing 3 MT-G2s will be better at is having a smoother beam.
Lots of options for the modders.
According to the graph, stepdown starts at 3 minutes. Yes, it does look a bit like 5. Time will tell what it really is, and what the actual output is.
I would not consider it a pure flooder either since spill with will be limited. But its certainly a flooder. (Not that I have seen the X60M in real life, but I can picture to some extend how the beam looks like based on my experience my MT-G2s in 10+ different reflectors/lights) X60M "only" got 69kcd before stepdown according to Acebeam. The "retard light" in this comparison is over 200kcd, its still a flooder in my book. As you can hopefully see in the pictures, its more about the beam pattern and less about the throw number. Or maybe I should say, its more about the lumen to Kcd ratio if you want to go the numbers route. Real life use, or beamshots is a better way to get an idea of how it actually looks, but when we only have numbers, might as well play around with them. Retard light have a lumen to kcd ratio of 57. Most would consider a 12x XM-L light to be a flooder despite that several emitters are de-domed.
In comparison.
K50, 1450Lumen, 188 Kcd (I prefer to use Selfbuilts numbers for that light). Lumen to Kcd ratio: 7,7.
X60, 5000 lumen, 155Kcd (Supbeam numbers). Lumen to Kcd ratio: 32
X60M, 10000 lumen, 69Kcd (Acebeam numbers). Lumen to Kcd ratio: 144
As you can probably see. Throwers typically have low Lumen to kcd ratio. Floody lights have higher numbers. The best thing is naturally to see lights in real life since these numbers does not compare outer spill light, general spill light, size of hotspot, corona, transition in brightness throughout the beam, smoothness, etc. But it can give you an indication, and I hope that can help you to get a better picture.