Hey, I'm a second year undergrad reading PPE at Oxford.
Your A-levels sound perfect. Literally, could not be better for Oxford PPE. The uni has no required A-levels for PPE, but Maths is recommended, and History is suggested. I don't know this for sure, but I would expect that your combination of A-levels are the most common among Oxford PPEists.
Economics A-level provides a good basis for undergrad econ, especially when combined with A-level maths. Lots of first year econ is taking the results you learn at A-level and deriving them mathematically, which is where basic calculus comes in really handy.
For politics, you have to be able to argue a point. Undergrad politics is very different from A-level; you take a big step up from describing the political world to actually testing those descriptions in practice. It's a lot of reading, and a bit of data work, but crutially your essays week-in week-out are arguing for a particuar position. Essay-based subjects are the best practice for this.
Then for philosophy, there's no one A-level that really sets you up best for this (no, not even Philosophy A-level!). It's a lot more technical than a lot of people expect; you really have to engage with the intricacies of arguments, and read critically. But as with politics, the end result is usually an essay that argues for a particular position, so any essay-based subject is a great start.
I'm not certain Oxford would particularly care about a modern language on top of those - you might be better focussing on the four. It may be fun to signal an interest via your personal statement, but always relate it to the degree (e.g. talk about an interest in French philosophy, political history of Russia etc). I think people overestimate how much Oxford cares about extracurriculars - they like well-rounded and curious students, but they don't need you to have 5 A-levels! Similarly, I wouldn't worry about your A-levels not being "rigorous" enough. No A-level work really stands up against undergrad work, and it's not really supposed to - all you're after is a solid groundwork and a keen interest in the subjects.
For background, I did Maths, F. Maths, Economics and Gov&Politics at A-level. Let me know if you have any questions I can help with, or if you need any advice on the admissions process!