The carnist here either
This argument seems to focus on trying to find the most ethical animals to eat, rather than questioning the underlying assumption as to whether animals need to be eaten at all, especially when the best foods for protein are plant-based
Ants aren't necessarily any better at converting food into meat than cows (given their exoskeleton is largely chitin - which is indigestible to humans), certainly probably not an order of magnitude better. So in that case, all the sustainability issues would still exist. Same with jellyfish: medusa farms probably, again, run into the same sustainability issues, but it's difficult to quantify given that they have essentially no nutritional value.
The fact that in the future it would be hypothetically possible to eat something without a central nervous system or that has a diminished capacity to suffer doesn't change the fact that right now, as we speak, eating meat contributes to animal suffering. So we can have an esoteric conversation on the side about some weird hypothetical, but it's important to recognize that this hypothetical is just fiction. You can't use any discussion or argument regarding beings that have no subjective experience as a means to defend the exploitation of those that do.