Having tried to hack my way through this pointless limitation, I've figured that it might be a bad code architecture decision.
By scanning the different configuration files I've found that the workspaces are actually defined numerically, that is,
workspace_2 etc... as opposed to have a generic
workspaces structure defined as an unbound set. So, in order to keep things manageable, they had to put this limitation in place.
This was probably a feature given to an intern or junior dev, based on how trivially it has been implemented. To refactor this, they'll need to put some non-trivial effort into it, so my expectations of this happening are really low. I just cannot understand how this could pass the review of a project owner, honestly.
Same boat here, as a long time Opera user eventually converted to Chrome, they have won me back just because of the workspaces... but already looking for a better implementation of this great idea somewhere else...
If there was a way to contribute code to this, I'd do it myself.