Set domain’s subfolder as root domain

Hi, we are using domain mapping from several years on a multisite configured with subfolders.
We actually manage hundreds of domains, one for each subsite.

Today we have a new need. Usually we point a first level domain to a multisite subsite, but now we would set the same domain on several subsites, using domain subfolders.

Example:
domain.com/it/ —–> subisite1
domain.com/es/ —–> subisite2
domain.com/en/ —–> subisite3
domain.com/fr/ —–> subisite4

Please note that the multisite is composed by hundreds of subsites and we would set it ony for few.

Is it possible? Otherwise, could you suggest some workaround?
Thank you