Do you get a new head with the milky upgrades, or do you have to send in your own?
He would probably open up the insides of your original L2 head on a lathe for more room. It wouldn't really make sense to retain the old head in stock configuration anyway, especially with the L2 and its very dated Luxeon LED (which isn't a good match for rechargeable cells anyway).
Of the Milky heads are they all flood lights, or do some of them have some nice spots that through a ways?
I gather that he can also make some wonderful throwers, such as the 'Legolas' (SF L1 host) or the 'Creemator' (E2-series host I think, not sure) for example. He would have to use smaller single-die emitters for those mods, as a smaller emitter area is required for good focus.
Legolas:
(very very exotic, I don't know the price, you know the saying, if you have to ask...
https://www.candlepowerforums.com/threads/204339
General Milky L1 information thread (very long)
https://www.candlepowerforums.com/threads/136976
Page 5 of Part 2 of his info thread will have some of the information that you're looking for:
http://candlepowerforums.com/vb/showthread.php?t=175864&page=5
I'm afraid I don't know very much about these mods comparted to others here, you could PM Crenshaw, he's had Milky do some nice L1 throwers for him and he'd know more about the possibilities there. If you want a decent thrower, you're talking about adding an optic or different reflector, etc.
But they won't be cheap, especially from an L2 host, which has a reflector on the floody side, as you already know.
You probably want to just e-mail Milky with a few questions, as this info I'm sending you is already second-hand. He might be able to recommend a budget mod he could do that would suit your needs.