Drop in VPN gateway, but keep my DHCP server

I have home network and remote site that I want to have connected. At home I already have favourite router which also provides DHCP and DNS etc. and want to keep networking as it is.

That's why MT2500 serves as Wireguard drop-in gateway.

This works fine from remote site to home network - being remote I can access devices and servers connected to home LAN (traffic from Subnet C --> Subnet A is fine).

To do the opposite, the instructions say about manual change in configuration, giving up the DHCP server from main router etc. I believe there is other option: I had once Wireguard running on Sinology server which was doing its job but was unreliable. It is matter of routing configuration, and that should be possible since there is full access to my devices?

Can I set routing on gateways so that devices from subnet C on picture can access devices from subnet A?

Hello,

The access from subnet C (remote devices) to subnet A (home devices) work ok (via the VPN), right?

The topology I think is no problem.
So I did not quite know what issue/request you have, please clarify one more