This idea came from some coliseum forumers. And I think, it would really not be hard to do.
There is an obvious lack of players in pvp in spiral knights. Most of the players from the game are interested in Pve, but the thing is that some are not even aware of the coliseum thing or they simply never paid attention to it.
Being a european player, I can see that there is almost no lockdown game during the day , even in the week-ends. There used to be some t2 lockdown but there isn't any longer and the t3 games are only in the evening. I think the t1 never existed.
Maybe because the new players are too focused on heating, upping their stuff and rushing to t3, they often don't even know there is such a thing as pvp in spiral knights.
In the same way as the new players discover the sprites, the crafting and else through the missions we could just add some missions at rank 2 or 3 for instance to introduce blast network and lockdown to the new players. I'm sure it would considerably increase the amount of players in the coliseum everyday .
I think it will be as effective as introducing the arcade to new players, since you can't force them to play a match.