You could easily modify many QRP kits by only changing the coupler.
Suppose the kit uses 10 turns on a toroid. That gives a 20dB coupler since the coupling ratio is proportional to the square of the turns ratio.
10 squared = 100; 100 times is 20dB.
So, say, 10 watts on the through line produces 100 milliwatts to the detection circuitry.
Suppose we now wind 32 turns on the toroid. 32 squared = 1000; 1000 times is 30dB.
Now 100 watts on the through line produces 100 milliwatts to the same detection circuitry.
It only remains to add a zero or two as appropriate to the analog meter scale; this could even be done "mentally" by remembering to multiply all power readings by ten.
SWR is a ratio so no change to the SWR scale would be required.
If the original coupler has more or less than ten turns, use the above simple maths to calculate a new coupler; for instance, an original 12-turn coupler will require 38 turns for a x10 change.
A x10 change is not mandatory; it can be anything but x10 gives simple meter re-scaling.
And, if the extra turns won't fit on the core used originally (the NorCal kit uses a "pig-nose" core for its "Stockton" (Sontheimer & Fredrick actually) coupler and 32 turns might not fit) just use a larger core or, in the case of the NorCal coupler, two small toroids or beads of the same material.