@soldamiani Hi Sol! Thanks for your response, and sorry that I am quite slow however.
There are some topics that would immediately come to mind.

1) Mirror glazes – I’d be very excited about an advanced mirror glaze course where they show small tricks to make glaze styles successful. I suppose it may be a long-shot because she has her own online pastry “academy” per se, but I follow Ksenia Penkina and she is amazing at this. Alternatively, I came across Magista entremet and Undecimo entremet on Instagram, and I think their work is pretty stunning, too.
2) Science of baking & recipe development – Though probably this is more obvious to the trained chefs or people with more experience, but I’d love a course about the science of baking with a focus on the recipe creation side (not sure such a course exists anywhere) – e.g. some comprehensive walkthrough on the principles behind certain processes, and how to choose ingredients, ratios and techniques best with specific aims and underlying processes in mind. I think this would definitely be helpful for people with similar aspirations/level as me. E.g., I came across the work of Paula Figoni (author of How Baking Works) who has a very interesting systematic/experimental mindset, or Katarina Cermelj – she has a book about how to make recipes with substitutions for vegan, etc., which is excellent. I bet that both would have a lot to say/teach in a course about recipe development and baking science.
3) Sugar work – I have done the course “Sugar Art” on Scoolinary which I quite liked, but it was a lot more about how to incorporate sugar into plated desserts than the sugar work in itself. I would be very thrilled to have a course about sugar alone (even from the basics) and how to get from relatively simple blown sugar or the pulled sugar ribbons to do very delicate sugar flower bouquets, etc.
4) Hyperrealistic cakes – As an amateur self-teaching person at least I think it would be so cool to have a course on main techniques and principles of making realistic cakes (similar to ones on “Is It Cake?”, for example). I have watched the Fruit and Nuts course (not sure this is the exact name) on how to make realistic-looking pastries, which I loved, and I think some other ones on similar subjects would interest me a lot. On the food looking like other food side, I think for example Cedric Grolet has very cool work, though I don’t have anyone in particular in mind for the food looking objects side.
5) Showpieces – I, for example, love the work of Amaury Guichon about chocolate work, and making very stunning showpieces. Maybe this is a similarly long-shot because he also has his Pastry Academy (though mostly in-person) but I’d like to learn how one can do and come up with similarly cool things as he or other chocolatiers do. Similarly, the sugar showpieces for me are equally interesting – I’ve seen some from this year’s Pastry World Cup and they were very cool. I’d love to see a course on them, the equipment they need, the tricks of how to create very nice ones.
6) Plated dessert design principles – This probably again is more for the less professional audience but may be great. I have seen similar courses available on plating canapes, plating in general, etc and found them useful. I’d be interested to see a version where they show the though process of design (e.g. Jade Nina Serkhel did a similar approach in her course for photos, telling principles and then walking through great examples of composition step-by-step with solutions to specific problems, which I liked).

These are ones that I could think of now – hope it is partially helpful. Sorry for the very long explanations – these may be highly subjective opinions/preferences, but I thought I’ll share just in case. 🤗 Thank you if you consider making any of these happen!