Yes, you could separate your DTM companies into separate Marketing Cloud organizations. This would allow you to have admins over each that would have no access to the other (unless you granted the user a level of access). The downside of doing this is that you'd likely want those DTM companies to be integrated into Adobe solutions in the same Marketing Cloud organization. If you were to take two different DTM companies that deploy Analytics that report to the same report suite, you'd likely run into issues with any of the auto populating fields in DTM (IMS org, Report suites, ect..) You might also have users become confused with logins since they would need to switch Marketing Cloud organizations to log into Analytics and DTM.
The other option might be to keep the web properties inside the same DTM company. You could then create a DTM group that mapped to the Approver + Publisher permission within DTM. After creating the group, you could map that group to a configuration in the Admin Console (Enterprise Dashboard). Once mapped, you could make user's admins over that group. Using this method would allow your "admins" to manage who has access to that web property. This also wouldn't give them admin level access to the other web property.
If you can tell me exactly what you'd like each admin level user to be able to do, I can try and give you suggestions on how to setup your organization.
Cheers,
Jantzen