Haha yeah, I like your idea though. I could probably machine out some bungs that are the like the factory quick connect so you could use the factory line or use a an bung, an to Barb fitting adapter.
Also, search for aluminum coolant surge tanks, that might provide some better results.
Thanks bud! I actually found a few on ebay.. Something atleast to try out.. Found a classy little tank for a MINI.. I'm sure what ever I find will be slightly less capacity but I'm pretty confident half a liter isn't going to show an issue.. Of course adding capacity would be amazing but don't think so :/