I think that as long as we buff clerks such that they don't directly replace jobs, we can go wild. People keep talking about giving them the behind the woodshed treatment, or just barely tweaking them so they suck less. Why? Are we forgetting that some of the most successful and prosperous empires in human history have centered around trade directly? Are we forgetting that a huge number of first world countries have been transitioning to a much more service based economy, rather than resource extraction? Clerks aren't required to be bad forever, just because they have been in the past.
There are a lot of ways that clerks can be buffed to be good, and a legitimate option. They can also be buffed to the point of becoming meta for a patch or two. Lets throw around some examples.
Example 1:This comes from earlier in the thread, but give clerks a .5% or .25% empirewide bonus to space resources. It would be a poor choice for someone going tall, but someone going wide might legitimately get more resources from running enough clerks to boost his space income than having them all be planetary jobs. It would reward having a wide territory, and make systems without habitable worlds more valuable.
Example 2:Boost trade power to 4 for clerks, and give them a 1% bonus to all specialist pop production on the planet. If you are running 20 clerks and five metallurgists, getting an additional 20% alloy production is pretty good, especially if you are running the consumer goods trade policy, and are able to use the energy and CG from trade to sustain the planet. You won't be swimming in CGs, but you also won't be spending minerals on it that could be going to alloy production.
Example 3:Make clerks a niche pick. Give them a planetary trade value modifier that increases with the proportion of pops employed as clerks. They would still be shit if you focus miners and technitions, but a purely clerk planet would get quite good.
Example 4:Boost trade power to 4 for clerks, give them techs to increase trade value much like how energy and mineral production gets increased, and leave it at that. Maybe still a bit weak, but better for low eco situations since they have no mineral upkeep, and aren't affected by habitability.
Example 5: This one is a bit of a stretch, but change trade routes to be interesting. Make it so that each system the trade route goes through would give bonus resources based on how much trade flows through it. For example, you have a planet with 50 trade value. So every system the trade route goes through that has exploited resources, like energy stations, mineral stations, etc, would give 50% of those base resources on top of what is already being mined. Note that this would count seperately, and would not be affected by technician production techs for example. So if a system gives 6 base energy, then having a trade planet beyond it and sending 50 trade value through would give a free 3 energy, which could possibly be increased by trade value increase techs like suggested before.
Example 6: Add inflation. You can make stupid amounts of money by late game, but all costs remain the same. You are just magically making energy/money pop out of the ether. If technicians are infinite gold mines, add an inflation mechanic that increases upkeep costs of all expenses across your empire (job upkeep, fleet upkeep, pop upkeep) the more you rely on technicians only. You make more money with technicians, but unless you mix in clerks, you fuck your economy in the long run.