I've been running both a Gen 2 and an early Gen 3 for quite some time with a 4S-LiFePo brick directly attached, without any problems.
I even managed to find one that fitted into my old NiCd MBP-1207 box.
Here Matt mentions that the light should not get more than 14 V.
You might ask ParkerVH if he still has Ushio adapters available, so you don't need to find an original Gen 3 bulb.
Sometimes you can even find a Gen3-like replacement kit for roughly $100 on ebay.
Gen 3 is certainly more fun, but a Gen 2 host with a Gen3- or an Ushio bulb might yield up to 7.5 Mcd (according to Annie
here).
I had only slightly flawed reflectors that time and got 6 Mcd at best, 5 Mcd easily.
But adjusting the bulb and measuring in at least 30-50 m distance is a real pain and eventually I didn't care anymore but simply adjusted according to plain eye sight.
Only disadvantage of Gen 2 high mode: if you want to stay safe you should give it a pause regularly, as mentioned by PBS
here.
I think you can have almost as much fun with a good Gen 2 reflector with Gen3-like bulb. Let alone you definitely need the later,
really good Gen 3 reflector anyway to get a noticeable difference.
(@The_Driver, thanks for recommendation, but I consider my knowledge to be quite selective. The best place - as always about MB - is here in CPF)