Interesting topic OP and some very thought provoking contributions from other posters.
My own life has had a period of both SAHM and WM. I was very high achieving academically and have a RG equivalent Honours Degree and and M.Litt. in a humanities subject. It might be considered a subject that is difficult to translate into a career apart from teaching it. It is niche and very competitive to really excel in. I have never taught and spent from my late 20's to mid 30's working in my field and loving it. I gained a lot of experience in these years but did not rise to the top of my profession - was always the 'next in command'.
I had dc at 35 and took 6 years out of work to be at home and I have absolutely zero regrets, they were some of the best years of my life.
We travelled extensively with dd - all over the place and we were often able to accompany dh on his work related trips. We experienced a lot together as a small family.
I went back to work in a very part time capacity (to do a favour for an organisation who were left in the lurch in the middle of a big project and they worked around my schedule for dd who was in junior school)
This led to another opportunity this time to become the most senior person of another organisation - I worked this position part time so I was always there for school pick up and afternoons at home. It was a stress as I did a full time role in part time hours for part time pay but it suited me. I did this for about 6 years and then went on to be the most senior person in another bigger organisation. And I am there now. Dd is in secondary school and either myself or dh are there every late afternoon when she gets out (working from home now anayway)
So, perhaps I was lucky? I got to do both as I wanted to but I believe having a really good degree and experience and profile before having dc really helped to jump back into the workplace.
I have always worked in my very niche field and love it so much. I'm very glad I went back to work when I did. I have no regrets.
I never felt I lost my identity in my 6 years at home - I was still me, I still read books, went to exhibitions, went to the theatre etc so always had plenty of things to talk about. I noticed some former colleagues really struggled with how to introduce me, as in 'This is Caperclips, she used to be......XX' . It used to make me laugh! Why wasn't it enough to just say my name?
I would be concerned for you though as I think it feels like you're running away from life outside of your house. And it would be a massive pressure on your dc to be the sole focus of your life. You may not be able to have dc or as many dc as you'd like. We had huge difficulties with a second pregnancy including infertility treatment and miscarriages so it's not always possible to plan.
I think it might be a waste for you not to experience all that life has to offer - there are so many jobs that might suit you with your qualifications. I have quite a few friends who studied both philosophy and psychology and they now do a range of jobs such as working as a workplace psychologist in a multinational, to being a philosophy professor in NY to being a psychologist in a top psychiatric hospital for the criminally insane..
I think you're very young to be making such far reaching decisions