My thoughts on your queries
@Lozza T
1. Either the Tekonsha IQ Primus or Prodigy options will be OK.... They have multiple setting savings so can be setup to suit each vehicle and setup at the press of the button without the need to reset everything.
2. Mirrors? Not sure about the Milencos but have heard good reports about them.
3. Annex Options. We paid a bit less than your quoted price two years ago for an Australia Wide one and very happy with it. Local quotes were similar or more expensive but advise you to make sure you look at quality and build before commenting.
4. Tool Box? They are brilliant! But agree with your thoughts and do a few trips and see how you go without one. It saves us carrying a lot of gear on the van floor or back of Prado and that gear is now already packed ready to go!
5. Reversing Camera? Have one on ours but use it while driving to see who/what are behind us and not for reversing. All wiring goes under the van from hitch to rear bumper so was an easy install.
6. Sway Bars? Or do you mean Weight Distribution Hitch? Both have their merits but it does all depend on individual setups. You may find the Triton needs them and the Disco won't and vice versa! As for WDH systems my preference/recommendation would be YES as they put more weight back onto the front wheels of the tow vehicle and improves the feeling of steering and braking. Unfortunately due to our setup we can not fit one so ended up upgrading the Prado's suspension to suit.
I'm sure there will be more
OH I am sure some on here will certainly give you some tips