Remote cluster as a "edge mesh gateway"

Dear All,
sorry, I don’t find the correct terminology, I guess. What I want to achieve is: have a single cluster publicly available to the internet, running nothing else then istio (and maybe Admiral), to route the traffic to our private clouds at AWS and IBM.
All the tutorials are for east-west traffic so I’m a bit lost here.

    PUBLIC CLUSTER                 (remote ?)
 ------------------------
 |         |            |
AWS  <->  IBM  <->  Legacy VM      (multi-primaries ?)

Of course, between AWS and IBM there are the eastwest gateways. Understood and working. But the “Public cluster” should do the “public dns” to “internal service dns” translation, with all the power of the routing tweaks like weighted routing etc.

Any advise?

We (Tetrate) is doing a lot of work in this space (will hopefully open source sometime this year). But our approach is to deploy mult-primary istios in each cluster and connect the VM to one of them. Also deploy Istio to the public cluster that then routes to other clusters istio ingress gateways. If you want to talk about enterprise solutions, feel free to DM me.