I am working on coming out with both a reproduction of the WW2 german smocks, slightly modernized (different pockets and such) in modern fabrics. And a reproduction of Russian Partizan Suits. Which is very similar in concept.
I already have the WW2 smock pattern done, just need to get 2 or 3 sizes dialed in, and I'll be ready to pump them out. I have about half the partizan suit pattern done. Both will have a few options, such as pocket options, to choose from.
After I get these done, I'm going to be working on a full-on SAS style smock, both a traditional one and a modernized one. Hopefully in ventile, 50/50 nyco, and some advanced technical fabrics as options.
I would love to find some double sided camo fabric for this purpose, at least for the pull-over smocks.
As for lightweight fabric, alot of those lighter weight fabrics are pretty fragile. Though there are some really nice modern fabrics in camo that would hold up well. The new fabric used in the new hot weather uniforms is pretty nice. I'm thinking about using that fabric in the smocks as a summer smock option actually. Strip it down with minimal pockets, it should be pretty lightweight.
I'm a huge fan of the pullover smock concept as a general purpose field top.
EDIT: If you want to go cheap, get a couple of oldschool BDU tops in a size or two bigger than you normally wear and use them as a pullover smock. Just leave them buttoned up and pull them on. You can get woodland or tiger stripe for summer, multicam for general purpose, and desert / multicam for fall / winter use. You can pick up new ones for $20-35. USGI surplus or Propper on Amazon / ebay. You might need to trim the sleeves shorter a little bit, but they work fine for cheap camo over-tops.