I'm not saying they made the wrong choice back when it was built, only that given today's sensibilities, cutting a city center off from its waterfront (usually) doesn't make sense from an economic or from an aesthetic perspective.
As for where else I-95 could go, I'm not very familiar with Philadelphia personally. I can speculate only from looking at a map. Assuming I was building it from scratch, my first thought would have been to route it east across the Walt Whitman Bridge, north where I-676 is now, then continuing north across the river on a new bridge to reconnect to where I-95 currently is. Or to route it along the west edge of the FDR Golf Club (as seen on Google Maps) and along the current I-76 routing, then east along I-676 north of downtown to where I-95 currently is.
While I will give you kudos for thinking outside the box with the above; here are some site specific issues:
1. The Delaware River is about a mile wide (with most bridge crossings roughly 1.5 to 2 miles long) in the immediate Center City area AND the land that abuts the east side of the river is NEW JERSEY
(Camden & Gloucester City). Your suggested re-routing would needlessly involve crossing state lines TWICE
for someone heading from the airport to Northeast Philly (as an example). Not to mention that EVERY Delaware River bridge crossing in the immediate area is tolled; $5 westbound for the 3 DRPA bridges and $2 for the 2-lane Tacony-Palmyra Bridge. If the Delaware River was as narrow as the Schuylkill River (which is only roughly 800 feet wide) and there was no state boundary to contend with; then that option would have some validity.
2. Your second idea essentially involves utilizing the existing 4-lane Vine Expressway (I-676), 4-lane Schuylkill Expressway (I-76) and the 4-lane Platt Bridge (PA 291). In comparison, I-95 ranges from 6 to 8 lanes. This option has been discussed and backed by the Get Rid of I-95
crowd but the primary problem with this alternative is that those roads (most of them older than I-95 BTW) are grossly undersized to be the primary artery: 10 to 12 currently available expressway lanes for all corridors
going down to only 4.
The only way this option COULD
work would be to widen EVERY 4-lane segment to either 8 to 10 lanes BEFORE removing/rerouting I-95
. IMHO, one would sooner see Former-House Speaker Nancy Pelosi becoming a conservative Republican than the widening of those expressways & bridges. It's worth noting that the I-676 Vine Expressway, particularly the newer eastern end (from PA 611 to I-95, that opened in 1991), is actually a downsized expressway
compared to what it originally planned to be.