30 pop for a city may seem like a good idea purely because that city is immediately functioning - and with an essence can provide at least 1 research (if water) - maybe an alternate solution is to go the MoM route and any newly settled city is pretty much useless for X turns.
Then its 30 pop to do 1 of 2 things:
Immediate outpost that allows buildable resources and can be upgraded - making an existing city stronger without diluting the benefit (but taking up a few turns to build).
Future city - start as a useless village, in 20 turns it becomes a city. Villages are defenseless and can just be stomped - and make it so stomping villages does not hurt relations (or a tiny impact).
This way its more of a strategic decision. Extends games a bit more but also limits city spam as villages are more of an investment in time and protection.
The other side of this approach is that it makes more sense to buff outpost capabilities:
Initial 30 pop is used for a smaller militia force, so a single sand golem can't steal an outpost.
Initial 30 pop is used for the production to develop the resources under the outposts influence - not affecting the connecting cities production queue - maybe at a higher rate of production (or fixed amount) with the idea that they are far from home and feel incentivized to work harder.(?)
Then you might WANT to build more outposts, and you're happy about the 30 pop to do so.