Lightweight.
Personally I would buy a lightweight stroller which can recline fully & then just take a car seat for the baby to be in during car travel. You can strap the car seat to the pushchair if you are in & out of differnt cars but when you arent needing the car seat it can be left at home & the lightweigth stroller will be much more practical.
I did a similar journey when my son was 11 weeks, 2hrs to heathrow & a 14hr flight to thailand, followed by 7 internal flights whilst in country. We took a trekker sytle pushchair & it was a pain & wish I had just take a umbrella stlye mclarens or similar