Making fussy cuts for applique will be a killer app. You are right. Having a list of fabrics that are cut and tested will be helpful as a demonstration of possibilities. I’d say most of the common fabrics for sewing will be fine, but specialized fabrics such as you are discussing are definitely worth investigating further.
The autotrace feature is interesting in terms of being able to edit it as desired. How are the designs or images stored for recall? It’s not totally clear to me yet.
In the interest of cross indexing, here are some topics.
Here is one of several topics that have discussed fabric. It includes actual product of Glowforge use on fabric by @Kusmeroglu of staff.
Wool felt will be a good a good material to use, although there are some interesting discussions as to contents of the smoke from felt.
@smcgathyfay has a good post with endorsements of fabric in one of the better topics regarding fabric.
There are several other topics that treat etching/engraving fabric too, like canvas or denim.