Since about Sept last year I have been using a pair of Dainese Dry-Line trousers with a set of thermals. I have just carried on using them because they are comfy, have armour and are waterproof so good all round. What I did not notice, untill reading a biker post, is why I was not getting any heat from the bike though them.
The theory goes that the thermals keep heat in but also keep the heat out. This guy had been to the south of France in the summer with no problem. I have been there in leathers and it is a nightmare once you stop.
Anyway while on a quick test run this afternoon, in shorts because I could not be fecked to change, I found I could not hold my legs on the bike. With the trousers and thermals no problems. Thinking about it now they have always been good for temp and no sweating.
Just an idea but it may be worth a try if your real hot. Nets and suspenders are an option for real bikers

and I get to watch.