I have multiple Bayswater bags (including the Apple collab version) and agree about how heavy they are with all my work stuff (I walk/take transit to work and carry my 15” laptop every day too). However, unlike the GP36, I can fit the Bays over my shoulder. I don’t find the GP36 to be any lighter than my Bayswater. I am not giving mine up, but I haven’t enjoyed using it for work.
After much trial and error, post pandemic I have settled on using a Clare V Le Zip Sac for days when I carry less and the large size
Prada ReNylon tote for days when I have to carry a lot. They are both lightweight.
Outside of work though, the GP30 is my favorite handbag ever and I regret not having bought one (or two or three) decades ago