add local VLAN on remote Subnet?

openVPN subnet 10.8.0.0/24

openVPN server at Site1; local LAN subnet 192.168.2.0/24
openVPN client at Site2 (shibby build tomatousb router); local LAN 192.168.3.0/24
openVPN client at Site3 (shibby build tomatousb router); local LAN 192.168.4.0/24

iroute and route statements are set on server, every site can reach ever other site, no issues.

Question:
At Site2, can I setup a VLAN and map it to a port on the router that is on the Site3 subnet (192.168.4.0)?
Basically, a port on the Site2...

add local VLAN on remote Subnet?