In a recent game I watched one player’s Millennium Falcon slam into a TIE Fighter, stop dead in its tracks, and get shot to pieces because of bad positioning.
Also, thematically, an A-Wing stopping a Decimator from moving makes no sense.
Here’s the idea in very rough form:
Configuration for Large-based ships only: Ponderous Bulk - Unknown Points Value (5 maybe? 10?)
When a medium or small-base ship overlaps you, roll an attack die. On a hit or critical result that ship takes one damage and acquires one tractor token.