Thanks all for your replies, much appreciated and a lot of great information to ponder.
I agree with those who said to go for spray-can primer, and it's much easier in the end and bottled primer just leads to messy and tedious strip-downs and clean-ups. But wider, even coverage for paint is what I'm really after so I googled around about the Paasche and the Badger...
Apparently the Paasche H is popular with car modelers because it basically sprays like a beast and is perfect for painting car chassis in no time flat. It's also simple, inexpensive and tough as nails. But more googling revealed that, if you're not laying down that sort of heavy wet coat its old-fashioned design does not atomize paint as finely as modern airbrushes, which leads to a more granular finish. I use acrylics and this seems a red flag to me. I'm also not thrilled with the siphon feed, bottles, etc. and cleaning and stocking all that in a tight workspace.
In many ways the Badger looks ideal; I like the gravity cup and in the US the price is really appealing, but I'm in Europe and it is a rare import which costs more than the Iwata so I had some serious sticker shock. Also, only the fine-needle is available which starts to make it look eerily similar to... the Iwata. Buying medium needle parts just sends the final price into the stratosphere.
Which led me to think (light bulb goes off, then slight embarrassment at the retrospective obviousness of it), Why not just put a .5 mm needle assembly into the Iwata and call it a day? Iwata parts definitely aren't cheap but it's dramatically less than the Badger set-up, and I assume the increased flow and a higher psi will get the coverage I'm after. And you can swap needles for fine work, 2 for 1, happy camper. If anyone uses this set-up for an Iwata I'd love to hear your results and if I'm on the right track here.