One basic mod is to replace the resistor in the tailcap to make the low mode either brighter or dimmer. The general consensus here seems to be that the 10 lumen low is too bright, so when I get a new L1, that will be the first thing I change. I really liked the 1 lumen low of the previous L1.
A more advanced modification would be to put new electronics in the head to bump up the power to the LED. I doubt anyone would be doing that though, since unlike the previous generation, you won't be able to fit two batteries because of the shortened length.
I have a feeling that other than modding the tailcap, people will leave this L1 alone until some new emitter comes out that causes everyone to want to upgrade again (like the Cree).