How to retain deltas when you change LO extractor in Production system

Requirement may come up to add new fields to LO cockpit extractor which is up & running in production environment. This means the extractor is delivering daily deltas from SAP R/3 to BW system .Since this change is to be done in R/3 Production system, there is always a risk that daily deltas of LO cockpit extractor would get disturbed. If the delta mechanism is disturbed (delta queue is broken) then there no another way than doing re-initialization for that extractor. However this re-init is not easy in terms of time & resource. Moreover no organization would be willing to provide that much downtime for live reporting based on that extractor.