Customer utilizes vpn translation with their Cisco asa 5510 to about 10 of their clients as the customers' internal ip range overlaps with their clients. Can we set up a 2nd MX as VPN concentrator and do something similar? I believe I have seen a document on this but I can't put my hands on it.
You mean like this?
Yup, it's supported in concentrator mode. It's just non-Meraki VPN it's not supported in.
I know it's a pain but I'd recommend checking in with your remote peers to see if they can do it. Otherwise, sadly, you're going to be out of luck.
VPN NAT for third-party VPNs is on my wishlist.