Let met go around the block. Three definitions first...
1. Aim Point. Where someone tries to aim a deep strike.
2. Landing Point. The point where the first model must be placed after scatter.
3. Landing Area. The total area near the Landing point upon which models are placed, with a possible extra 1 inch buffer if there are enemy models nearby.
Note : 1 or 2 is likely what GW meant by Entry Point. 3 cannot be a point as it is an area. No one should be talking with certainty as if they know what GW meant by 'entry point' as there is much sincere disagreement.
Using the above definitions, here is one possible outline...
On deep striking, the unit owner selects an aim point.
If this original aim point is within 48 inches of the beacon, a disruptor beacon 1d6 roll is made. On a 4+ the beacon owner chooses a new aim point, but it may not be in impassible terrain.
Whether the aim point has been altered or not, the full deep strike rules are applied identically as per 40K base rules, starting with a scatter roll to determine the landing point, then looking for the various things that might cause trouble if they are in the landing area.
My opinions...
The Fluff at the start of the Deep strike mishaps paragraph (Page 96, 40K core rules) state that deep strike into a jammed area ought to be dangerous. I dislike the alternate interpretations that go squarely against the fluff, that try to make 'landing under the influence' safe.
Rules wise, the various 'safe' versions of the beacon rules try to impose limits on where the unit might be placed that are just plain not in the book. On a 4+, they may be placed anywhere but in impassible terrain. Period.
Common sense wise, the unit only deeps strikes once. The beacon is a scrambler device which confuses navigation on the way down, during a teleporting process, or as a tunnel is being dug, etc... There are not two landings, two beam downs from the ship, or two tunnels being dug. It is beyond belief that after one lands near a beacon, one then instantly digs a new tunnel that comes up twenty scale feet away. The risks of landing in one zone should in no way effect or influence the risks of landing in an entirely different zone. It should not be safer to land in a zone selected by the enemy than it is to land in a zone selected by friends. The owner of the disruptor beacon should not have more control over the scatter process or selection of the landing point than the deep striking unit owner, or if he did somehow have a greater degree of control, he would not believably be using this extraordinary control to make the landing safe for his enemies.
Thus, for reasons of simplicity, not having to invent new rules, being compatible with the fluff, and just having the results being vaguely believable, the Beacon should simply change which player selects the aim point.