Hi, I would suggest that you ask these questions at open days (if you have the chance to go). They will be able to give the most accurate information informed by insider knowledge.
From what I can see, Oxford PPE recommends Maths but doesn't require it. Have you looked at the TSA? I don't think it has much (if any) of a Maths requirement so I imagine you'd still be in with a very good chance of doing well there.
I would worry less about the weight and more about what you actually want to do. Do you enjoy economics? Or are you thinking you would put up with it to get a degree in PPE from Oxford. I wouldn't recommend that at all, don't do a degree you know you won't love. Is philosophy what you really want to do? Then I would say do that.
Also look into philosophy and politics courses at other universities if that is what you really want to do. Don't sacrifice your subject for Oxbridge (please). LSE do philosophy and politics as a degree (which is a very reputable uni). So do other universities that have very good reputations.
I'm currently a biochem student at UCL. I could've applied to Oxford for biochemistry but didn't because I didn't like the course. I ended up applying to NatSci at Cambridge because I felt pressure from my school to apply for Oxbridge. Thankfully, I didn't end up at either of those universities. I know people doing both courses, and I now know for sure they wouldn't have been right for me.
Please choose the best course for you (at a uni that is pretty reputable). Don't sacrifice your passion for Oxbridge. I may be completely unfounded in this advice and actually these are just your two favourite courses right now, but as PPE and Philosophy are actually pretty different degrees, it seems to me that you have your sights set firmly there. However, if you genuinely love the idea of one of these courses and it looks good for your rough career plans - then of course you should. Wishing you luck with your applications 🙂