Well, obviously that 'solution' doesn't work if you haven't yet completed the Citadel DLC...so I can't verify that your solution does in fact work.
However, I did manage to complete the Omega DLC mission (man...I'm not sure if I reached double figure reloads to get past that dreaded final fight in that...definitely over half a dozen reloads though! That was tough! I'm not sure that I could easily replicate winning that final fight either...just dumb luck, maybe?).
ANYWAY...here's how I managed to beat the shopping mission...I reloaded to a save prior to entering Harrot's kiosk. I remembered that I had found a rare omni-tool in Mass Effect 1 and had in fact upgraded it to include a teleport capability. So, when Harrot first suggests that you find Aria's couch for him, I made sure to use my upgraded omni-tool in order to take Harrot's exact coordinates in the precinct.
Then, when I found Aria's couch and Harrot pays you, I just made to sure to use my omni-tool's teleporting upgrade to zap Aria's couch on top of Harrot! It worked a treat! When I got back there, I had Harrot's money and Harrot was dead! Under a couch! Beautiful!
P.S. anyone else die after exiting a kiosk like that?
Weird.