HI, I really don't understand the hole picture, maybe you can tell us the problems you want to solve to try to help.
As workspaces are really easy to work with, your idea is really good. Just a few comments.
Try to use the labels, that can solve most of your problems, specially with calendar. For example, if you have all your sales related events with a "sales" label, you will be able to see only them when you need it.
Same to personal and company staff. Labels are one of the most useful parts of FO.
Also, I can see you have only one person in Marketing, for that reason, unless you have public and private staff, the marketing workspace is redundant. Just create the workspace of the person.
If you need to other people to see marketing staff, then your idea is perfect. All the public staff goes to Marketing and the private staff to the person workspace.
For calendars, there is an option to see the calendar of one person or all at ones. For the shared calendar you need, you just have to set User = everyone and that's it.
Just one last thing.
Maybe is better if you use colors instead of sub-workspaces. For example:
Instead of
Sales
User 1
User 2
Marketing
User 3
Maybe you can work with
User 1
User 2
User 3
And use color to identify. For example: red = sales, blue = marketing.
It is really useful and gives you more control about your day to day work. Try it and tell me how it goes.
Daniel.