It might not be as stupid an idea as you think, but certainly not in the next five years.
But 5-10-15 years down the track, why the hell not?
We need to believe the NRL will continue to grow, and hopefully now they have a commission structure in place that actually enables them to have a real strategic focus - markets like a second team in Melbourne must be on the list of potentials.
Think about it: Melbourne could easily support a second team with its population. TV coverage must (surely with the next tv rights) improve that will do nothing but further raise awareness. They have a state-of-the-art stadium. The derby clashes between the two Melbourne teams will sell out - guaranteed - twice per annum. Ratings from Melbourne for big games such as Origin and the Grand Final are crucial in allowing the NRL to compete with the AFL for coverage. Two teams will only assist further in delivering these ratings.
If Sydney are going to have two AFL teams, I cant see why its so impossible that Melbourne will have two NRL teams.
People need to start thinking a little more optimistically at the opportunities. Sadly, a result of the NRLs short-term, risk-averse nature over the last ten years has robbed us of any real belief this stuff is possible.
Perth must be the short term priority, as should be the Central Coast and perhaps another Brisbane team. However, don't discount Melbourne within the next 10-15 years. Maybe earlier if the next TV rights bonanza gets done. If they sell it short again - then heaven help the NRL.