> Now I want to add an outside client into the mix (e.g. my laptop). I want to be able to connect to just one of those hosts and have that host forward my packages to the others.
> I can get it to work if I pick _one_ specific jump host but I haven't managed to set it up in a way that I can connect to any of them.

You might consider setting up just one of your servers
as a gateway for a subnet dedicated to your client machine(s).
Then add routes on your servers to the gateway.

For example, set up 10.0.0.1 as the gateway to 10.0.1.0/24,
and set your client machine up as 10.0.1.1. Machines on
10.0.0.0/24 remain connected directly.

If you need to be able to route through any one of
your servers on an ad-hoc basis, then you'll need some
additional routing protocol magic, as Matthias suggested.

Cheers,
Phil