Hoodie as a garment is made for colder weather in general. Hoodie should be warm. 100% cotton will not keep you warm due to structure of jersey textiles and cotton as a substance. You are right, 50/50 is just the cheapest what you can get, however there are "healthy" blends that work perfectly while being functional.

80/20 and 85/15 is a perfect combo. 20% of polyester will give a hoodie required function of being warm, and 80% of cotton will make it breathable. But you have to consider that fleece jersey can have a brushed or terry finish. Brushed fleece feels more warm due to open fibers and more thick. Terry fleece feels thinner even being the same weight and not as warm as brushed. But terry will work perfect for summer nights.

Brushed fleece can be single-brushed and "multi"-brushed, normally triple. The more it's brushed the better feel it gives. Also it peels off less. Cheap hoodies from H&M and Gildan comes with open fleece non-brushed, thats why they leave fibers on your t-shirt.

And final is a weight of the fleece. More is better. Standard is 280gsm. Btw for people who don't know, GSM stands for Grams Per Metre, so it's a physical weight of the item. Some hoodies with being 350gsm can weight 0.8kg. Cheap 50/50 hoodies will be around 350-450 grams, because they have 50% of polyester which is super lightweight as a material comparing to cotton.

And final. 100%cotton hoodies don't "work" as good as blends of 80/20 and 85/15. So no need to overpay for good blanks chasing for a perfection. Do your research and charge for a quality, not only for your brand. I am surprised that many new "brands" don't use blanks from Continental, Salvage, Earth Positive, Stanley/Stella. My personal recommendation is to look at Continental as they are part of Fair Wear community and easy to label as they don't have a neck label, only size of the garment. This is not an advert and I don't work for them 🤘

Hope this helps to take a direction.