Just because you don't like it doesn't mean you should put it in.

I was classed a Kickboxer and now do K1 and have won 2 World titles and beaten some of the best in the world.
Wont really go back to KB unless defending my Kickboxing World titles.

Condition yourself that's all you have to do lol.
Lowkicks are a good weapon to disable mobility that way you would get more Thaiboxers wanting to compete to try and stop the fluidity and speed of Kickboxers.
Original Kickboxing had lowkicks in anyway, otherwise you should call it Freestyle Karate Extreme, or Extreme Freestyle Karate.

I dont get you want knees but no lowkicks!!
No boots and shins which means Shin Conditioning but no Lowkicks because people dont want to condition Thighs!!
Also is it going to be no clinch and points score more over power and aggression to lean towards kickboxers than Thaiboxers?

I think you need a good rule set that is equal for Kick and Thaiboxers otherwise you wont get many that want to do it thats why the K1 Rules are good.

Clinch and 1 Technique (Knee, Kick, Punch, Throw)
Lowkicks
Stomps
Spinning Backfist
Continuous fighting.

Points scored for Power and Aggression, but also defence and counter
Points deducted for running away
No points scored for tippy tappy techniques

A lot of big named orgs are already changing Full Contact Kickboxing by shortening the rounds (5x3 or 7x2) to get fighters to be more aggressive and with shorts and without boots etc.

Maybe that is the way you should go, same rules just shorter rounds and different equipment.

And wasnt KBX 8 man already tried before when they tried getting Lex Easdon, John Orchard Fran Zucalla and some others together in a Middleweight 8 man comp, but it never happened?

http://youtu.be/PyF2tZB0lUA