Yes. You can create multiple MDM servers in ABM. You can even set model types to automatically assign. For example, let's say that all your Macs are to be managed by Jamf while all of your iPhones are to be managed by Intune. You can set auto-assignments to make the product types go to the proper MDM without manual assignment at time of purchase. You can also create multiple VPP tokens. You need to create a location for this. Once the location is created, you can reassign app licenses or acquire additional ones and assign to the location token of choice.
Please note, migration of existing device, especially if they are supervised, will not be easy, especially for iOS devices. For Macs, you can issue an unmanage command from the current MDM and then run a sudo profiles renew -type enrollment command on each Mac. This will allow automated enrollment into the new MDM without erasing the device (this assumes your reassigned the assets in ABM and you have admin rights on the Mac). However, with iOS devices, you will need to nuke and pave them to achieve supervision via automated enrollment.
Hope this helps.
Reid