I flew several pax during my time on the mighty Jag and I can honestly say I never set out to make anyone feel ill. My intention was always that they should enjoy the experience as much as possible.
Unfortunately if you're not used to it, flying in a jet (and all the factors previously mentioned) is just so alien that it's very hard for your body to put up with it!
The fact of the matter is that unless you take off and join the TACAN hold for an hour or so (even that might be too much for some!) there is no way to avoid pulling G and putting the aircraft into flight regimes that are slightly more exotic than you would experience on a Ryanair flight!
The other thing that I noticed was that you could never tell who was going to be able to handle it and who wouldn't. The biggest shock I had was a big, burly PTI who I was convinced would have a cast iron constitution was blowing chunks (sorry!) within half an hour.
Everyone I ever took flying, regardless of how many bags they filled, had the time of their life and wore a huge grin for days afterwards. I think that if you've never been up before, the sight of valley walls flashing past up close and at speed is something that'll stick with you for a long time.
In short, if you get the chance - take it. You don't know what you're missing out on!
Final point - can only vouch for my old aircraft type but Low Level IS allowed for a maximum of 30 minutes per sortie but shouldn't be generated solely for pax purposes.
BV