Sorry, but I think this is a rather stupid thing to suggest may be added in the future. Smiler is a Gerstlauer Infinity Coaster, which is basically a more advance version of a Euro-Fighter. So its like having a big box of lindt chocolate, then considering buying a cheap knock off which doesn't taste as good. Which would you rather?
There's no way Merlin would install a Euro-Fighter at Alton when they already have an Infinity Coaster (which is essentially a Euro-Fighter on steroids) at the park.
I would however like to see Rita replaced with a Mack launch coaster of some sort but I'm not sure that Dark Forest would be the most ideal location for a full-blown Megacoaster in the guise of Helix.