You're definitely right. A good aroace character's story doesn't have to be about a relationship, nor does it have to be about being aroace. It's just a question of how the author wants to communicate a character is aroace, without needing to state it outright. Stating it outright makes it feel forced or tacked on.
But Slimy_Boi_Enigma earlier gave some really good examples of how to get around that. (And I feel silly for not thinking of those options, they're really straightforward)
The other question of course is how central the author wants it to be to the narrative. Both a story about an aroace character and a story about a character being aroace can be entertaining, but there is a difference and any artist looking to join the project might be interested in knowing which version of the story the writer wants to tell.
I also get Freemints30's argument.
It's not a bad idea, but what more is there to the story? What's the hook?
But those are just my two cents on the matter. Either way, I would be interested in collaborating on something like this, but I'm already having trouble keeping up with making my own comic, and I don't have any sort of fame to help the author spread the comic.