I'll keep my solid crank arms, thank you. If I want to save weight, I'll eat less and lose more weight.

I know Shimano has some really smart R&D engineers but a glued part for this type of application seems a bit risky to me. Constant flex, movement, vibration, rain, etc. I think that could work against the crank over time - but what do I know...

There are plenty of examples of solid crank arms that broke on vintage cranksets. However BITD, we did fuss about it so much. And those cranks got a bad reputation for the brand very quick.

Here are a few.... https://pardo.net/bike/pic/fail-001/FAIL-001.html

unfortunately they don't do https. So don't be clicking on stuff once you get there.

Yup, I had one break on my 1974 Raleigh Super Course about a month after I bought it. When I took it into the shop the owner was skeptical but replaced the crank. I then asked him for a job - which he obliged! My first bike shop job in 1974.

Not about cranks but my ‘80s Raleigh Technium
Tri-Lite uses epoxy to join aluminum main tubes to steel lugs, a head tube, and rear stays.

Wider arms aren’t necessarily stronger. They could be stronger or stiffer, and in different directions.

A whole lot of “all other things being equal” is needed to cover all the other possible changes of cross-section, but itš too hard to qualitatively discuss them all, much less quantitatively. A quantitative statement about it at least can be evaluated qualitatively, but it probably won’t be quick, accurate, and cheap.

Adding a few more parts similarly might or might not be a true improvmet