I wouldn't wear them, the force of your 60+kg landing on top of the baby in an accident is enough to cause a lot of damage, let alone the force of the impact.

I'd be inclined to use a capsule of some sort. At least if bub is strapped into that it's the capsule bouncing around in an accident and taking the brunt of it. I'd probably put it behind the drivers seat.. maybe on the floor like Lulu said, to prevent going through the windscreen.

We are probably going to Singapore early next year and i've been told they don't use car seats there for their kids.. My kids are bigger tho, so not sure what to do there... maybe we can get hold of some basic boosters.. just to raise them up so the adult seatbelt won't be so deadly??