Since RPC interface does not scale to serve a multi user service.
In absence of better alternative, the interfaces used by a proprietary extension are usually the same as in P2P consensus.
POW is used to figure the longest chain and until now broadcasted transactions were assumed the one and only.
These simple rules ensure a consensus between the proprietary stack and the border router, and that is the consensus I referred to.
IOW, assume every transaction your "border router" gives you is now the
one and only true transaction, and everything conflicting with it must
go.
You are right that the assumption about the one and only transaction have to be relaxed. Broadcasting
double spend only if it is actually replacing an earlier - for whatever reason, would simplify internal consensus logic .
Tamas Blummer
Bits of Proof