Any Suggestions? (Bootcamp related)

Hey guys,

So my Macbook Air has only ever had OSX on it. I've dual-booted Windows on it before a while back, but soon realized I didn't need it.

I use it to edit video on the go, so I want to retain as much space on the SSD as possible (128GB) before I archive footage onto an external.

Nowadays, I've really been into a PC game called Marvel Heroes. It's about 10-12GB large. This is the ONLY reason I now want to dual boot. A Mac version will be available sometime later this year, but I don't really feel like waiting that long.

Before anyone says "but MBA's aren't meant for gaming", I know. I have a proper gaming PC at home. I will only be playing this game on my MBA during trips and I don't care if it only runs at 15fps on minimum settings.

Do you guys have any suggestions as to what route I should take in terms of preserving as much space as possible for OSX on the MBA while also having Windows in Bootcamp?

I was thinking of just installing Windows and ONLY Steam/Marvel Heroes in the Bootcamp partition. Nothing else. I also wouldn't mind spending money on something like a 32GB SD card permanently in the SD slot, but I'm unsure as to whether or not the transfer speeds on an SD card are even fast enough for that option to be viable. Will it? (about 10GB on SSD for Windows partition and the game will be installed on the SD card)

If there is no other alternative than just installing the OS and the game, I'll just do that. Just trying to see if people have tried any unorthodox methods of getting their game on with limited space.