So you want 3DGS to be your client-side front-end then, eh?

In that case, I believe your best bet is to make a translator DLL that takes the 3DGS data/packets and turns it into your servers format and can then read the server info/packet and turn into 3DGS. Conversely, you could program your server to receive 3DGS data do what it is servers do and then spit out 3DGS data.
I guess you could also eliminate the 3DGS network model all together and have the DLL do straight Client/Server stuff....

I've never done or thought of this BTW, nor do I remember anyone who has, so this is opinion, not fact.