We tried that and that's how we eventually got them to switch - 2 years later. The client required a feature to start 'live sessions' with mobile subscribers whenever they were active on the network (made or received a call) and support for multi-level menus. The original architecture was transactional and they understood its limitations. The rewrite used SEDA and we were having latency issues, gc and memory issues handling live sessions with SEDA. So we had to do another upgrade to switch from SEDA to Actor based model that worked. The next upgrade was small and incremental compared to the first one very and we had the system ready by the time contract was finalized.