Well, at that rate, you'll only be getting maybe 10-15 minutes of operation (even less the more you use >100A (also remember the higher the current draw, the less energy you get out so the less capacity and the less runtime even beyond using it up faster)), so if you provide a way to cool the pack, even something like potting it in PCM (phase change material) (whihc would also help prevent water ingress), it might not matter much, other than the energy loss to heat decreasing your capacity.
The cells themselves, per that linked article's statement:
The JP40 has a 45A true continuous current rating and a 60A “temperature-limited” rating. You can run the cell at up to 60A but you must stop before the cell gets hotter than 75°C (which is HOT!).
are really only 45A cells without generating their own problematic heat, so you should consider it at best, say, a 250A pack, if heat is a concern. Probably should be kept lower than that (you'd have to check the test data on that article to see if it has a current at which it doesn't generate notable heat).
The Nickelplated copper would be less heat generative than the nickel; as long as you have something that can weld that to your cells with low enough resistance connections to not generate heat at those points.
If you build the pack as a big block that's 7 wide and 14 long, and use a series strip on every cell (so 7 of them), it will minimize the load on each strip, and maximize the energy you get out of it.
If you have to build it in osme other shape, then your current might be limited (regarding heat) by the narrowest path from one group of 7 to the next in series (as this also means that the parallel connections will carry current, when they shouldn't need to, and so they also will generate heat and cause voltage drop under load).
There are some threads discussing nickel/copper sandwiches, and nickel-plated copper, and ohter alternate interconnect methods, successes, failures, etc., and various welders' performance, that will probably help you when you get to the point of having designed the pack's layout and casing and such.
