I suspect manually exporting the keys would not be required, merely rescanning, and it could be triggered by a wallet version change f.i., which would then do the same as a "-rescan" option.

This needs to be tested of course, but as soon as the base coin to clone from is known, I could give it a try. Preferably something without too many customizations, so it can be cloned within a reasonable time frame 

I think the reason it was not done is that it was more work when you did not have a tool that could give you the balance of all addresses. Also noble does not have too many addresses with balance, this would be much more complicated for litecoin f.i., and quite impractical for doge or bitcoin.

Another reason is that an exchange-based swap practically guarantees coins will be lost and never swapped (all those that overlooked the swap news), and I suppose at least some coin devs had that in mind.
Speaking of which, an exchange-based swap destroys anonymity, as the exchange knows your email and IPs (and may leak these unwillingly if hacked or seized at a later time)

About the division by ten, another good reason would be to get away from not just the satoshi value, but also the integer 64 overflow and floating point precision issues. Dividing by 100 or 1000 could also make sense.