I'd like to add that the knock-on effects of adding or changing rules are really not that extreme in most cases, when it comes to combat rules.
For a random example, I grabbed an equipment supplement a few years ago and started adding some weapon traits. One of them was "Cruel" weapons which are designed to shatter in wounds and leave behind bits of shrapnel. I don't remember the rule exactly without looking at it, but I believe each shard reduced maximum hp by 1, and there was a Medicine check to remove the shards, increasing in difficulty for every shard in the wound. Also, there were degrees of success, allowing some shards to be removed but not all of them. A failure by enough could leave scarring (permanent hp loss) or aggravate the wound (now you are bleeding)
It is a little much to keep track of, but it is there and adds some extra danger to a fight.
I even have played around with something called Baatorian Green Steel, which would increase all of the Cruel numbers by 1 (increasing hp loss, DC to remove, ect) and giving a character the poisoned condition if they have shards in their body, maybe based on a Con save vs how many shards you have.
It is minor, but I didn't want it to be a big thing. And it wasn't hard to put together.