From past experience I can say that a 180mm Mono Trials is way more powerful than any rim brake setup I've come across on a mod. There isn't much play on a mod wheel, wouldn't worry about that. As for a profile, yes it's possible but you may have to do an adaptor bodge since the disc mount on the hub is in the wrong place. If you want to go rear disc, don't get a 6-pot Hope, get a Mono Trial. It's more powerful, lighter and doesn't come with a floating disc.