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I've done this a few times too and have used an elaborate set of house rules. Basically, every wound is labeled with a severity level based on the HP stat of the wounded person. After a week with the wound, a HT roll is made for each wound to see if it improves by one severity level. Critical success improves it by 2 levels. I have a list of modifiers to the HT roll that includes severity, level of activity, missed meals, treatment by physician, etc.

Regeneration automatically reduces/removes the wound at an interval determined by regeneration level. Magic healing works similarly.

Every wound has an effect on character performance depending on severity level, location, HT, and in some cases, wound type.

Bleeding is a major issue for characters as each wound bleeds separately and bleeding rolls depend on wound severity both in frequency and degree of modifiers. First aid (or surgery for some hit locations) can be used to stop bleeding but it is rolled for each wound (modified by location, severity, equipment, etc.).

Surprisingly, It doesn't slow the game significantly. This is because I, the GM, do all the work. I just describe the situation in non-game-mechanical terms and the players roll with it.

The only thing I don't like about this system of house rules is how long it took me to make.