The trick of waiting for Indoorsman and getting Outdoorsman at the same time is still functional as of 10th March 2011. I've added this guide for anyone looking for exact instructions on what to do.
1. Start a new game in 72 Hour Mode.
2. When the chopper drops you off, walk into the door next to Carlito.
3. Go through the Security Room and out into the mall (Entrance Plaza).
4. At this point you get the cutscene where you first see Brad and you're told to get something to help barricade the door. Instead of doing this I just stood by the window on the balcony overlooking the car park outside and waited for my Indoorsman achievement to pop.
5. Once Indoorsman has unlocked, return to the Security Room the way you came and save your game on the couch provided.
6. When it then pops up advising that the game has saved successfully and asking if you want to continue playing, turn your XBox off (I used the guide button but I expect it'd make no difference using the 360s power button or a remote control).
7. Turn your 360 back on, start Dead Rising and choose Continue Game. Outdoorsman will pop as soon as you're back in the game.
Be aware that the game will auto-pause if your pad switches off so you'll either need a play and charge cable or wired pad to do this. Others have suggested rubber banding your wireless pad so that Frank keeps moving but I can't confirm this as I used a wired pad. The steps I wrote above are exactly what I did. Any questions or clarifications feel free to contact me.