As others have said, I’d play with routing/IP forwarding such that being VPN’d to one machine gives you access to everything — basically I would set it up as a “road warrior” VPN (but possibly split tunnel on the client [yes I know, WireGuard doesn’t have servers or clients but you know what I mean]).

Alternately, I think you could do some reverse proxy magic such that everything goes through the WireGuard box — a.lan goes to service A, b.lan to service B, etc., but if you have non-http services this may be a little more cumbersome.