Looking forward to that update
OK here is the gear I'm taking - plus some thoughts al alternatives and some small changes.
This is my current idea - we will see how it fares in May. But based pretty much on my general gear. This is for long trips where the exact conditions can not be predicted and can/will vary.
Base layer that is ALWAYS the same. Moto-Skivees riding shorts (which are excellent) and also their riding shirt (though I will also carry a thin knitted silk shirt as a backup). But any wicking base layer will do. Cotton is useless as it stays damp.
Then mid layer -
For cooler days a Buffalo Systems Special-Six shirt
Special 6 Shirt - This is sort of sweater sized and can be squished down with ease. I will be buying an UNLINED hood for it when I am in the UK. This will then fit inside the helmet for neck draught protection I have used Buffalo gear for years - it is seriously good kit. Breathes but is wind-proof to 50mph and shower proof.
For more temperate days I will be getting a Buffalo Windshirt (and hood) whilst in the UK - These pack into next to nothing.
Any warmer - no mid layer needed.
Legs - knitted silk long johns. Again these pack into nothing. Think aerobics/yoga tights.
The Protective Layer which will always be the same - I have a Buell Adventure suit. No longer made. But it is a non-waterproof suit with lots of CE protectors, anti abrasion and with really excellent venting. It is fabric which goes against my person preference these days - but I have it and it works.
I don't know the US marques so well - but in Europe there are equivalents from the Jofama Group (Halvarssons and Lindstrands) in Sweden and Rev!it in Holland. There is an interesting write up on the Revit Sand 3 suit on webbikeworld - where they discuss the concept of non waterproof gear . Gloves - Short CE certified from Halvarssons. Halvarssons and Revit gear is now ALL CE2. Pricey but good.
Finally a run of the mill waterproof outer shell. Simple. My Jacket is made by Bering (I had need of a Jacket in the UK and that's what was on offer) - Pants I discovered I had a pair of 3layer Goretex Mountaineering pants sat in it's wrapper - They fit over the Buell pants so perfect. Wet Gloves - Triumph branded waterproof/lined gloves. Ideally the Jacket would be similar - but I do not see enough rain here to justify the cost (to me). My waterproofs are packed in the top case all year.
Basically the only thing that could bulk up my cases is the lined Buffalo shirt.
In the past I have carried 2 sets of gear (warm/dry and cold/wet) and it is simply impractical. And that's what most of us do - "Ooh I need a good vented Jacket" - And "Ooh I need a good warm/waterproof Jacket". Both usually are either too cool or too warm.
If I thought it was going to be VERY HOT (by that I mean hours riding above the mid 30's °C) I would add a cooling vest to the pack. I will NOT be taking one with me next month.
Boots. OK a bit of a compromise - but I do suffer from my feet getting cold so I will use tall lined and goretex hunting boots from Chiruca in Spain and also wear Sealskinz merino lined goretex lined socks - knee length. But I will have other walking boots for casual use any way which I also use on the bikes. So it's not extra gear.
I know the above will work from 0°C to over 40°C - dry to extreme rainstorm
Just some thoughts. May be they are of use - maybe not.