Some thoughts:
Merging the rosters would be problematic for people who agreed / want to participate in one but not the other. They are very different projects with different levels of commitment involved.
If someone wants to make a comic adaptation of a text battle, they can do that within the Colosseum series already anyway (I think). Even if they wanted to make it part of Fight Club, that can be handled on a case-by-case basis and doesn't warrant actually merging the two projects as a whole.
Our two projects are different enough that they would have different audiences interested in them. Many people may be interested in the comics but not in the text stories, and vice versa. Putting them in the same series would likely just mean pushing content on readers that they're not interested in.
In conclusion, I see a lot of potential problems and not any real benefit to merging the projects.
As far as them working symbiotically instead of as rivals, I'd say they already do that. It's not like there's any real competition or animosity between the projects, and each one provides different opportunities for those interested. Just because they are separate doesn't mean they can't complement one another 