you ran out of /24 Ips - ok then how about a /23 or /22 ;)
The jump from /24 to /16 is nuts. You use that as your mask on your devices or you just using it as a routing summary?
To be honest that is not here or there to be honest - but it one of my trigger points is all ;) Insanely huge networks used for no valid reason.
The only thing you need to do is fire up another instance.. The details of which are up to you, the really the only thing needs to change is has to be an actual different instance.. so another port say 1195, and use say 10.0.183.0/24 as the tunnel network. Then create your rules in your openvpn interface for 10.0.182 and 10.0.183 that limit or allow what you want those clients to be able to do.