If I understand the proposal correctly, it is only to insert a command to lower reps. Therefore, the effort required to achieve full guard rep will still have to be put in.
This will not make it any easier to get hold of a guard ID...it will make it easier to get a guard tag, but, as one can mount a non-guard ID with a guard tag, one would assume the reverse were true.
As for Mule's hypothetical bribe/drop situation, it is gonna be awfully expensive and can be done presently by aborting missions in place of the rep drop command, anyway.
Running 'round to random parts of Sirius to guard tag that cap is one of the most annoying things someone can do (Tale of the Bismark?:lol:)...and, now that NPCs have gained more resistance to CDs and friendly fire, it is gonna be even harder for some characters (Hunters, enemy pirate groups, factions like Mollys) to have the correct NPCs shooting at them in a fight.