Sorry for the slow response.
Yes, the triple padding is worth what it costs.
Mine may have taken as long as it did because it was a custom pattern. They had the pattern, at least, which is more than Cronkhite had (even when Glen was still working).
As to wearing out, the construction looks to me nearly identical in the details to Cronkhite's construction methods. The material is very heavy guage Cordura nylon (which is what separates it from the polyester cheapies), and all the stress points are sewn through thick full-grain leather gussets. The zippers seem even heavier than those used by Cronkhite. I'm not sure what there is to wear out any different than with the Cronkhite bags.
My oldest Cronhite-made bag is a Reunion Blues, sized for a Miraphone but I used it with my B&S F tuba. I traded an Altieri bag for it to a guy who wanted a top loader (I have always preferred side loaders). That was in 1992, and it was well-used even then. So I can absolutely confirm the longevity of Cronkhite bags.
Removable shoulder straps is another option with Gotz, and I recommend it. You are right that the straps are the weakness. I bought a pair of backpack straps to replace them (the camouflage looks a bit strange on the black bag, but I don't care)--maybe $30 on ebay. They were used on military backpacks and have an overload release (presumably to prevent the enemy from dragging a soldier by the pack from behind), and I put chain links through those to prevent accidental release. But they are well-designed for comfort and adjustability, and cheap.
And I bought a Red Oxx "The Claw" for the one-shoulder strap, which is simply brilliant. The padding is molded onto that strap, and ultra-non-slip in addition to being apparently indestructable. The clips suggest that the 125-pound rating is not fictional. Also $30. [url]
https://www.redoxx.com/claw-shoulder-strap-92008/p]/url] I carry the tuba over one shoulder only because that Red Oxx strap is so secure from slipping.
That said, there is nothing weak about the straps Gotz supplied, they simply aren't that comfortable.
Of course, shoulder straps on a Cronkhite are not replaceable without cutting rivets, and there is some advantage in that simplicity.
What I particularly like about the Gotz Supersac is that it is cut to minimize bulk, as you mention. Ray Grim came back from Germany back in the deeps of time with a wood case that oriented his Miraphone 186-CC bell and lead-pipe down and left-side outer branches up. It had a curved top that made the case much more compact than the typical wood case that has a bunch of extra space above the upper bow, next to the bell. The Gotz bag is cut that way, even though it is carried with the bell on the top. Your picture shows that, but it's more pronounced on my tall-bell Hirsbrunner kaiser. Also, the side-opening design means that one side unzips, rather than a clamshell zipper around the middle like Cronkhite and Protec. The zipper runs down the edge of the side panel, and around half of the bell. It's a good design that provides excellent access to the instrument.
Rick "wishing he had a need for gig bags right now" Denney