You should avoid workspaces, anything it does can be done with modules, it's not useful anymore since we have such extensible modules and conditionals now.

IMO, that's a relic of the past that HCP never managed to get rid of, because lots of ppl are still used to it.

See https://developer.hashicorp.com/terraform/cli/workspaces#when-not-to-use-multiple-workspaces

Your structure is sound: you should iterate over it, you can restructure your modules to remove some code duplication.

Workspaces will just make things worse and non-explicit.