You can have multiple HUBs in fact, the biggest question in your case is, if you choose another MX as a HUB and remove the current HUB, will you be able to access all the Auto VPN features?
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.