I just have "Bike Gear" as opposed to a set for each season - and you can get all four seasons in a day (even going over a single pass) in the Alps, one early August day we went up the Nufenen pass, turning up from the Swiss side it was cool and damp, like a wet autumnal day, at the top about 0c, a dry cold and snowing a little bit with gale force winds, by the time we were down in the valley on the italian side it was 30c and humid.
Hence I use a textile suit with outlast liner as it works from below 10c to above 20c with just a light baselayer, consistently hotter and out the liner comes, I then carry a light micro-fleese to layer up and down so I am OK down to about 5c, I take a selection of summer / "3 season" (Lined but not too bulky) gloves and combined with Heated grips I tend to wear the coolest I can get away with and use the grips if I get a bit chilly.
I have on occasion carried a mesh jacket, but found if i had it I never needed it, and if I did not take it then I wold have 2 days of 40c to deal with, but I also learned at this heat nothing keeps you cool, so I tend not to bother.
I sometimes yearn for better ventilated textiles, like the ones with seperate waterproof liners, but these tend to "wet-out" and weigh a ton / take forever to dry / flood your hotel room overnight, and are then cold and wet the next morning.
I personally don't like being really bulky either, so with the exception of the now antiquated practice of commuting I would just not go out in the depths of winter, if I need to dress to the point I can barely move it is not much fun, coupled with shit on the roads, low sun, risk of ice etc. I just don't see the point and typically stay off the roads December - February and save my fuel money / tyres.
Also with the Alps you rarely "Have" to go over a high pass that's freezing cold and can take an alternate valley route or whizz through a tunnel.
I think the OP's idea of "summer" gear is workeable, I think a good waterproof laminated suit with a quality outlast liner would be ideal, as would probably be fine 90% of the time without layering up or down, my Mrs feels the cold a bit more than me but can sit in a sauna and not sweat, so she can do a 2 week tour of the Alps in summer without ever removing her liner.
I have had trips where my liners were out almost the entire time, others were they were in the entire time, and some where they were in some days and not others.
Since having laminated textiles I have bot really bothered with Waterproofs, had about 3 hours of torrential rain on last years trip one day and stayed dry with the exception of hands - yet to find genuinely waterproof gloves, so I carry a couple of pairs and when they are both sodden I just put up with it, or just go back to non waterproof ones as they don't feel as soggy, and turn up heated grips.
ALso wateproof oversuits tend to be very clammy, like a boil-in-the-bag suit for people, so unless it is very cold and very wet I find them pretty useless, but if going to the Alps in May I would make sure they were packed!