picking off the last couple posts here, I had an idea on how to fix this utility vs aesthetics problem in battle sprites. if you have two battle sprites, you can equip one as a "costume". you still have to upgrade the auxilliary one if you want the ultimate's aesthetics (just like you have to upgrade to 5* gear if you want to use it as costume), however you do not need to if you like the low level look. additionally, more battle sprites could be added as "cosmetics", for example a universal battle sprite that resembles those generic-looking ones found at the Lab, as well as in the ending section of "The Collector" mission.
I like this idea, it's the simples solution to the problem, the devs shouldn't have any trouble developing this. But i still like Phelyne's suggestion in https://forums.spiralknights.com/en/node/125321 . I don't think we should have to buy and level up a second pet just to change a cosmetic variation.
Being able to have a snarblepup (not like I have one lol) by your side even when using the Drakon skills sounds cool, or even using cosmetic baby pets while having the full grown ups' skills.