Here was my idea to help with the research queues being lost on scientist death that could be modified to also work with the construction efficiency being discussed.
Basic version:
All creation of either a Research Plan or a Research Center. The former is an abstract idea (like a fleet) while the latter is an actual building you construct, but they work identically. They have
- A scientist
- A specified number of research labs
- A research queue
Basically it works like research queues do now, but the queue is assigned to the plan/center rather than the scientist. If the scientist dies, the center idles (with a notification) until a new scientist is assigned to it. If the new scientists cannot manage the labs assigned, the excess are unassigned, ready to be used elsewhere.
The same thing could work with construction, only with the different officer type.
Immersive version:
When a new scientist/builder is assigned, the research/construction bonus is set back to 0%. Then every construction cycle, it increases by X% such that after 5 years (or whatever), it will be the full bonus for that officer. This represents all the normal "new job" acclimatation (learning the new facilities, hiring/training new junior staff, bending the bureaucracy to your whims, etc)
However you can also assign a 2nd officer as a protege/apprentice. They don't provide any bonuses to research/construction, but they start that timer as soon as they're assigned. So, if the lead scientist dies after only four years, the protege is already 80% ready of the way to full capacity.