I've done cross cloud connects where the cloud vendors are on the phone with me and eventually say "We really don't have any idea why the tunnels are not connecting". And that's when using Cisco VPN appliances, no less, following everyone's setup instructions to the letter.
Indeed, not a trivially solved problem yet.
I would be worried about downstream issues with the security architecture, especially down the road when you pick up clients with compliance requirements.
"3DES in combination with MD5 is a common candidate..."
If a security architecture is a priority, then these people will not be customers.
Triple DES is not "boring crypto" by any means.
https://news.ycombinator.com/item?id=13383006
Wireguard's crypto is boring. That's the point.