1) Is there any guidance anywhere on how long Thaumaturgical rituals should take? Is it just arbitrarily determined by the GM? Also, is it possible to make up Complexity gaps by taking extra time (as per the sidebar on pg. 316)?
"A minute or more," according to YS261. It seems, though, like that's the minimum time for the general ritual and prep work--once you get down to summoning up the energy and channeling it into the spell, each step of the process is one exchange if you're measuring in combat time.
2) It seems like making Workspace rating equal to Resources minus two makes them next to useless unless you have Resources 2 or higher. Declarations have a base difficulty of Mediocre, after all.
That's the default level for a general-purpose workspace that you're assumed to have accumulated without even trying. It's not terribly hard to afford a better one with a Resources roll plus a few invoked/tagged Aspects if you're willing to put a little work into it, and you can have a slightly better workspace by limiting its focus.
