Namecoin testnet beta

I would like to create a new branch on namecoin/libcoin. The branch would be namecoin-testnet-beta, the beta part is to indicate that it still uses some hacks to let it sync.
I've not checked the details, but is the need for the new `isTestnet` argument due to testnet starting merge-mining immediately, while Namecoin started it only later?  If so, could this decision be made by adapting `adhere_aux_pow` in the `Chain` subclass instead?  This seems like the proper place to do it, if possible.