Why not one class of small NEP orbiter-surveyor for every outer system moon, and fly ten or twenty missions of this class, before we bother thinking about landers?
There's only so much data you can gather in flybys.
I don't think NASA has the budget to launch 23+ orbiter missions, regardless of how cheap and generic the orbiters are. Anyway, I think if you're going to spend a large fraction of a Billion dollars just getting there, it makes sense to spend a bit more to make sure the payload is optimised for the job. Each one of these missions has a good chance of being the only one of it's kind for one or more generations. Better to do it right the first time.
We are entering an era of cheap launch costs. Duplication of a design costs near-zero, all the price is in the fabrication capacity, the design, the testing, the engineering, keeping a subject-matter-expert control team on standby to make executive decisions for a few hours a month, and the remaining launch costs.
In practice, the Space Shuttle Transportation System, fully ammortized, cost about $1.5B per launch to loft 15 tons to low orbit in practice.
Falcon Heavy will launch about 40 tons for ~$100M, a factor of 40 improvement. The Russian launch vehicle Proton-M was already at about 20 tons for ~$100M, and Atlas V 552 about 20 tons for ~$200M.
There's only so much data you can gather in flybys.