The MX typically does not play any significant role in the BYOD solution. The onboarding runs through manual enrolment or through the MR access-points and provisions the client into the SM Mobile Device Management.
Best to build a test-system for all your intended devices as there are some gotchas that make it less usable compared to an ISE. For example, the BYOD users can automatically get a certificate for WLAN access. But this is not an intended use case for your domain-users which need a different authentication. And these certificates can not be used on all switch ports.
If you have an all-wireless, all BYOD environment, then it will be great. But if there are a significant amount of legacy devices you need "something else" for these. And the ISE could give you all at the same time.
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