I absolutely agree that the weight is much more important to ergonomics than many seem to think, but I'd agree with ezbass that balance matters a huge amount too. I built a headless bass from a 'Samba' wood body and cherry neck. The body is incredibly light and the neck heavy. The strap buttons are not placed quite right and it neck dives really badly. That makes it feel heavy, even though it weighs an absurdly light 2.6kg - which in bass terms is nothing at all.
Also, the weight can differ substantially from instrument to instrument as the wood varies considerably - being a natural material. Take a look at Peach Guitars - any guitar over a certain value (about £500 from memory) will be individually photographed and weighed. You can see as much as a 1kg variance between two otherwise identical guitars.
I'd be tempted to take the plunge into headless if you can stretch the budget. My strandberg is 2.3kg for example. It feels like it weighs nothing because the balance is so good. It will probably be about the lightest wooden guitar around, and they do a strat-style variant in SSS or HSS with a vibrato. The Ibanez Quest you mention would also be a great entry at rather less money, though still possibly more than you want to spend. I'd not worry that the hardware is proprietary as pretty much all the headless guitars I'm aware of (save for the 'copy brands') have excellent quality hardware. Strandberg's hardware is fantastic, and if the Ibanez EHB bass series is anything to go by, the Quest hardware will also be brilliant. Certainly no upgrade need.
