[volguus zildrohar]

Unlikely to happen due to cost-to-value situations. That stretch of the Market Street Subway would have to be closed for various intervals if not for an extended period to allow work to be done. To do so would be to impact The El and the five subway-surface trolleys that it carries disrupting transit all across the city because the route is so spinal.

A better case could be made if there weren't already two trolley stations within that stretch. Yes it requires a transfer but it's better than a seven block walk.