For now, it makes sense only to run once all the missions of the veil just to see where the anomaly will be. And to farm those parts people always would run the fastest mission (Gian Point).
We have 6 mission on which MK3 Lavan and Vidar parts drop. Why not split the drop by mission?
For example: on the early 3 mission (with a lower lvl enemies) you'll have a chance to receive Reactor, Shield Array and Engines; for the last 3 missions drop could be more specified, like on the one mission you can get Vidar and Lavan Shield Array on the other Vidar and Lavan Reactor and so on.
Also/or make those relic an additional drop. For now there are a lot of missions wich runs much fuster and more effectively to farm relics. Don't think that people playing railjack mission to farm relics.