I wear jerseys with sleeves to cover up my base layer with sleeves. If you really want crash protection, you have to wear a base layer. I have some wool blend base layers that are very good at wicking sweat, so one of those in combination with a lightweight plastic jersey is the best combo I have found for hot weather. I tried a compression base layer this summer and it was miserable. I imagine it would have worked really well had I crashed.
As far as going gloveless, I do it all the time. However, if you plan on falling down, it’s a lot better to have gloves on. Palms take forever to heal.