Those contemplating change here may want to review what happened after Newt resigned as speaker after nearly losing the GOP majority in the ‘98 elections. It was said by all Bob Livingston was going to be Speaker... until Larry Flynt took him out. Dick Armey was next in line as majority leader, but passed, as did the whip Tom Delay. Dennis Hastert as picked as someone all could accept, but not as anyone who could have been predicted. Delay later was speaker, and a decent one, until rat shysters took him down. If Boner falls it would become... interesting. Those pushing for his removal DON’T have to have a replacement beforehand, just they don’t require an Obamacare replacement to vote it out. Requiring such up front is a false card tending to support the GOPe. There WILL be people interested in taking the job with large enough egos to think they can do it, likely several such. The caucus will sort them out. Although they’d best be thinking of contingencies.
DeLay was Majority Leader for a while, never Speaker.