You could use an OPC-to-OPC bridge. For instance ICONICS DataWorX32. The product allows you to configure registers that have an input (source opc tag) and outputs (target opc tag).
The process values are only sent to the outputs on change. This allows you to have thousands of tags without causing too much load on the network. You could download it to give it a try.
I think it involves licence fee from Emerson, they normally do not third party residing on their network, pl check but Delta V is using only iFIX for their HMI.