DOT botched that when they let the new apartment complex abut the highway so close.
EDIT: I misread what you're suggesting because you said "dedicated lane on Rt-2". I'm having trouble visualizing exactly what you're talking about. However, I don't see how making some sort of direct connection between Alewife and Lake Street helps. The Lake Street ramp is also a mess during peak hours.
The issue with the Alewife exit traffic is the garage entry/exit, which backs things up into the general route-2 gridlock, contributing to it.
The other big problem with the inbound Alewife intersection is the bottleneck at the lights. People turning to go east on Route 16 towards Medford have two turning lanes, which backs up and blocks the cars trying to go west on Route 16 past Alewife. Those going west get cramped into one lane that then reopens to two at the light. There ought to be two lanes for both eastbound and westbound Parkway traffic, but I don't know if there's the space to configure that.