If you decide against running Molisks, and rather would try Argonaut, my advice is to still leave the Molisk in there, just don't put points into the Molisk DNA. Molisk would still spawn, just at a slow rate.
If you remove any of the Molisk DNA you can't get it back. Whether you like the mob or not, that LA is geared up to be a Molisk land. Destroying the Molisk DNA will imo destroy some of the value of the LA. Obviously, if replaced by a better mob, that would increase the value.
At the end of the day, you bought the LA to promote it, and provide some spawns for the community. If I had 99 people wanting to hunt Argonauts and 1 person wanting to hunt Molisk, I know what I'd do.