In the May 5 online VRE chat (
https://www.vre.org/about/online-forum/ ... /2021/May/), one passenger specifically mentioned the 73-minute gap between morning trains on the Fredericksburg line. VRE's reply: "We are actually making plans to return to full service and will be able to announce a date soon."
When Jay Westbrook of CSX addressed the Virginia Association of Railway Patrons annual meeting in 2007 (
http://www.varprail.org/2007_meeting.html), he mentioned that the CSX Fredericksburg line was at capacity but also mentioned improvements that were under way. The new Potomac Bridge wasn't mentioned; it wasn't even a distant dream at that point, I guess. I think he also said that the line wasn't full around the clock, but weekday rush hours had no room for more trains.
However, I don't think that VRE shuttles to Metro would be a workable answer. The fare systems are completely separate. Transferring adds 10 or 15 minutes to a trip: at Franconia-Springfield you have to go up and over, at Alexandria down and under, and at Crystal City cross the street and walk about two blocks, plus time waiting for VRE or Metro. And shuttles wouldn't occupy space on the Long Bridge, but I think they would tie up the mainline while reversing direction. If they terminated at Alexandria, just sitting there wouldn't help. They would need to move off to AF interlocking, sit there, and come back again, meaning four moves on the mainline. Or they might arrive and depart Alexandria with no schedule padding, probably hurting the Metro connection.
At VARP's 2015 meeting (
http://www.varprail.org/2015_meeting.html), Thomas Hickey of VRE said that VRE was looking at moving toward regional express rail. I don't know whether the 22-month study he mentioned ever happened. Up to that point VRE had consistently insisted that there was not enough demand for weekend VRE service. VRE had also stated on its website that its core business was bringing weekday commuters to the business district in the morning and bringing them home in the evening. Later in 2015 VRE told VARP that possible weekend service was premised on population growth and increased demand.
I think VRE could adapt to changing transportation demands, and I think that CSX would be open to running the same number of trains but in a different pattern. Whether VRE really wants to carry anyone except commuters, I don't know.