So with a single address we can just do dumpprivkey. What about a denominated one? It will probably have hundreds of addresses. Is there any command to dump all privkeys from a darksend/denominated wallet?
Not to my knowledge... you have to dump each address individually for the private key.
Is it possible to code this kind of option into a wallet?
Once your DRK have been Darksent to whatever number of rounds you're happy with, just put them all back in one address and dumpprivkey for that one address.
Let's say the DRK all started in one address, would sending all the funds to a single address increase the likelihood of the Darksend funds being followed? How probable would it be that funds starting in one address and split into 25 addresses are all sent through 8 different addresses (for example) and then end up at the same address again? Following it manually (or even thinking about it) would be a very confusing affair but I imagine it may not be impossible for a computer program to pick up on this sort of pattern.