A long-awaited plan to overhaul one of the country’s worst-funded public pension systems was introduced Tuesday in the Kentucky Senate, setting the stage for debate on one of the defining issues of this year’s legislative session. The bill introduced by Sen. Joe Bowen was notable in part for what it didn’t contain. It excluded some key provisions contained in an earlier plan endorsed by Gov. Matt Bevin. The new measure would not force any current or future state employees or teachers to move into a defined contribution 401(k)-style retirement plan. That was the cornerstone of the plan Bevin wanted lawmakers to consider in a special session that never happened last year.