Now, four years later, the horse is out of the barn. (And in full gallop.) So it's really too late for a Republican plan.
The time for a Republican health care plan was before 2006, when the GOP controlled both houses of Congress and the White House. If not then, at least they could have proposed some of these measures back in 2009 when the ACA was being crafted. But they didn't. In fact, they chose to boycott the whole process. (Which looks really foolish in hindsight.) So now we have Obamacare and time will tell if it works or not.
But, really, for the time being, it's settled. And the GOP really needs to find another issue. (Pssst! Try immigration reform.)
* And, by the way, it could never get passed. Tax employer-provided health insurance? Yeah, that would go over well with the millions of people who currently get their insurance tax-free at work.