Current draw from cells is usually in terms of the cell capacity versus the hours it takes to discharge. So a 1C draw on a 15Ah cell would be 15A for an hour.
Generally the C ratings are very close within the same chemistry and form factor. But even if they differ here they would have to be *extremely* different to not handle a similar draw from a cell with more than 2x the capacity.
That is to say, the new cells could only have half the C rating for discharge and they would still be better than the originals in the same configuration.
If you use 2 to replace 5, the C rate would need to be about the same. But if the only difference is 2mm thickness, is seriously consider slight modification of the module case to make a little more room.
Cooling may not be an issue if you're not in a hot location, but it might actually be less of a concern if you can do the 5 cell arrangement.
I can't give much on the internal wiring, but I THINK the modules are actually wired in a way that allows every cell to be individually monitored so changing to a different arrangement might not be possible.
2012 Candy Blue FFE, 100K+ Miles
33.5kWh battery pack, 26.4kWh EtE
40A+ L2, CHAdeMO, CCS pending