Now, I don't disagree that this argument has merit, but...
It's also the argument for bringing Wasps in in the first place, and for encouraging both teams to work together at the Ricoh long-term. Of course the figures aren't absolute, either - Wasps coming in wouldn't have been a total uplift as they'd have taken some from us rather than it being a both, and us coming back would now take some things from Wasps.
If I were CCC, I'd be arguing that due to the actions of our owners, Wasps were the hedge that were brought in to cover said loss, and that due to the actions of our owners, Wasps are more reliable partners.
Now, I'm by no means saying don't use the argument, but do think about how you'll cover how it'll be used against you. I'd argue the main case you have to make is the potential from a successful football club is far more. Not only that, but in terms of the intangibles (identity and association with the city) CCFC have something there that no other sporting club have.