Light rail is only called that because of its passenger capacity. It can actually run at speed of heavy rail like the Path and MTA. Just ride the Newark Subway Line after peak hours and you will be on trains that are booking it from downtown to Bloomfield.

If your issues is headways, Newark's subway (the older of the two lines in the light rail system) runs every 3 to 5 minutes within Newark's borders during rush hour and every 10 minutes during the off peak business hours, before transitioning to every 20 minutes until 11pm. This extension would probably just follow that style as this is being proposed to relieve congestion, and having shitty service won't alleviate anything.