There is considerable effort on this direction already. A lot of the bus (on board computers, power, etc.) is standardized for a lot of missions. But there's a

There is considerable effort on this direction already. A lot of the bus (on board computers, power, etc.) is standardized for a lot of missions. But there's always have uncertainty in the payloads. First, because there are lots of contractors involved. That's somewhat fixable. Second, and most important, is that many of these payloads are cutting-edge. They've never been built before and some of them push physical and engineering limits. I've worked on missions where the only delay was the payload for many years, and they were simpler than JWST. It's a problem of not knowing what we don't know. When working on those kinds of systems, the estimates lose a lot of meaning.