Having only previously installed CVP 3.X...
With CVP 4.X and SIP I want to have an ingress dial peer first pointing to my CUPS server. Then configure and second dial peer with a preference on 2 pointing directly to the CVP Server (In case CUPS fails).
Is this feasible, are there any issues with this?
I understood where you were coming it is something we put in place for 2.0 and 3.0 in the early design guides but eventually dropped because of some potential issues and recommended to use HRSP on the GK instead(basically what happened as an issue was that callers were continually calling since they were dropped whenever bandwidth usage was above the set limit, since this RAS failure due to the bandwidth used, calls were routed via the dial peer preference to the CVP directly creating further bandwidth usage hence we ended up in a nightmare of high number of call setup and eventually dropped and the CVP servers completely brought out of service, basically defeating the original intent, better consider an additional GK and HRSP).
What you might consider for your failure scenario is routing directly from the GW to a Unified Call Manager SIP Trunk or for the previous releases directly to a UCM extension, not sure if the SIP SS will be in partial or out of service, but you need a CUPS to route those calls via SIP in the current CVP environment.