Workspaces are great already but as another awesome enhancement I suggest that workspaces have their own custiomizable start up options. Present start up options are good themselves, but we just need to be able to choose different start up options for each workspace.
Let's say I have a main workspace I use for most spontaneous and random stuff. I would probably keep my new blank page start option for that.
I also have a workspace for web developement projects that I'm concurrently running. I want all of the tabs on that workspace from the last session to automatically open so I can continue working on them directly.
I have just another workspace for frequented domains I look up information in (MDN, Youtube etc.) so I want to have their main pages load on start up so that I can start searching in them directly.
All start up options for these are present in opera, yet I can choose only one and that will apply to all workspaces. So a separate start up option for every workspace (if preferred of course) would be a nice enhancement.
I dont know if out-of-focus workspaces consume noticable resources, but if so, it could be set up so that each workspace starts up with their setting when they are opened for the first time in the relevant window.