Well, considering I don't know your customer's topology, let's address some important points.
A non-Meraki VPN doesn't participate in Auto VPN, so if you have a non-Meraki VPN configured on Site A and want to access a resource on that VPN through Site B, you won't be able to.
As I said, I don't know if this is your case, because without topology details, the rest is speculation.
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.