But the problem is, nobody has defined the steps for ECDSA signing (well, until I did so but that's a different matter), so as far as ECDSA generation goes, it's the wild west out there.
That's actually a pretty good idea to start using Tagged Hashes for ECDSA nonce generation too considering RFC6979 is rather slow and expensive. But you have to slightly modify the algorithm to find a way to be able to generate more than one k in case you want to grind to get low r values to avoid 33 byte r in DER encoding.
The solution that is necessary for this is some algorithm that guarrantees a unique number is taken from a set of numbers (which have a high chance of collision).
Technically you are not selecting a number, you are generating a random number using a random entropy. Considering the output is also 256 bit, there shouldn't be any collisions.
