Hi there! I'm in a somewhat similar situation (not an attorney, but I'm an older student with a lot of career experience making a career change). I did a lot of due diligence before applying, including taking a bunch of professors out to coffee and picking their brains, meeting with grad directors, and talking to friends who have been through the process and now have tenure. and have been accepted at a few places and I thought it would be helpful if I passed along my experiences. Feel free to DM me if you have any specific questions.
I'm going to preface this by telling you that I didn't apply to any Top 10 programs - all of my schools are in the 20-50 range, and even those schools had different reactions to an older student seeking to make a career change. So if you're looking to go to Princeton, I don't have anything for you. But on the whole, the best advice I can give you is to think about your entire application package (your work experience, your research interests, your writing samples) as a story that you are trying to tell the admissions committee. Are you seeking to study something related to your work as an attorney? Has something you've dealt with in your career sparked a question that you want to answer? All of that can build a compelling narrative that can turn something that could be seen as a downside into a huge upside for you. Spend a lot of time thinking about how you want to package yourself, and each of the elements in your application package should support that narrative. In real world terms, you are writing a proposal to a potential client - you are trying to sell them on you.
To address your questions specifically:
Re the writing sample: Do folks dust off and revise UG papers, or spend time researching and writing a new paper altogether? I'm not remotely opposed to the latter, but would welcome any suggestions you all can offer.
If you have something that you can stand behind that you wrote over 10 years ago, then you might be okay. I ended up writing something new. If you decide to write something new, think back to the work you've done as an attorney - is any of that work at all relevant to your research topic? If so, use that as a starting point and write something related to that. Then, in your personal statement, reference your writing sample, why you chose to submit it, and why it's relevant to your application.
How does work experience factor in (if at all) to an AdCom's decision making process? I don't see how someone with my background can compete with a candidate of the same age range but who got a MA in PS or worked in a similar field. I am wondering if the JD/years spent as a lawyer has any appreciable merit. (I do not harbor any illusion about how much a law degree is worth outside of, you know, the law).
This is where your research interests can help. Ideally, your research subject is related in some way to your work as an attorney. You should use this to your advantage and talk about it in your personal statement. For example, talking bout how working as an attorney led you to ask questions X, Y, and Z, and now you're applying to graduate school so that you can answer those questions. OR something like that. I can tell you that two of the schools I applied to were really interested in my work experience and two of the schools didn't care. So it'll probably vary for you.
Is it self-sabotage to state in one's SOP that one does not want to be an academic? Does the desire to pursue a non-academic career post-doc make someone with my background more or less desirable?
Probably. Schools want to educate future scholars. They are going to be less likely to give funding to someone who doesn't plan to use their degree to do research. That doesn't necessarily mean that you need to seek a tenure track job after you finish - maybe you want to go work for a think tank or something. Based on my experience talking to different schools, some places are more okay with this than others. In the end, it would help if you asked yourself this question - why do I want to get a PhD? Based on all of the advice I've received, if the answer isn't related to wanting to do research for a living after you finish school, then you might want to reconsider applying.
I'm leaning towards American or theory, but I've read horror stories about theory candidates having fewer options after their degrees are conferred than a HS drop out. If not pursuing a teaching pos, does the subfield matter as much?
I can't speak to this question, but am curious if others have something to add.
Any suggestions on programs for someone with my background? I don't feel the need to pay too much attention to the rankings. I'm open to the DC, Baltimore, PA, NJ, NY areas.