As an aside, it's always nice to hear someone who recognizes they aren't a good fit to be a manager. I'm not sure I would be good at it either but it seems that even people who very obviously don't have the personality for it tend to jump at the opportunity.
I speak from experience from being around vindictive people.
That doesn't sound realistic, for a couple of reasons:
1. 1:1 meetings between a manager and their staff happen on a regular basis, e.g., weekly. If HR had to attend each of these meetings, they'd never get their own work done. (HR's job is to cover the company's ass, not yours.)
2. If your employee walks into your office for a 1:1 meeting and finds someone from HR there, they'll freak out because they'll think they're about to be fired. (That's a typical situation where managers call HR for backup.)
I would agree that it might be a disadvantage for women, but conversely I would just make an effort to ensure there was _someone_ else with us, male or female. So instead of drinks 1:1 outside work, or a 1:1 meeting, It would instead be three people which mitigates both parties liability.
I am a senior engineer, not a manager, but if I were a manager one on ones would be necessary, I would attempt to have HR in each 1:1 as an ass-saving measure anyway.
But then again, I believe I would be a poor manager so I don't wish it on anybody.