In Yosemite, (how) can I save an entire Space/Desktop (or a collection of open programs and windows, like a Space)?
The paid App "Moom" (£7.99 Mac App Store) can save and restore desktop layouts (amongst other window related tricks). I don't think it actually starts applications though, but if they are already running it will arrange them for you. You might be able to combine an automator action to run a bunch of programs and then have Moom arrange them for you?

I have multiple applications open for marking student work (browser, word processor, text snippets, marking app etc.) and use Moom to give me a consistent layout for marking each type of assignment. It works well for this.