1) If it doesn't have the accessory socket already installed, that is a good addition. In addition, I installed an accessory socket "Y" cable and SAE cord that runs power up under the tank and to my tankbag without any wires hanging out. At the least, you can get an accessory socket to SAE converter, an SAE extension cord, and then an SAE to cig lighter socket if you want to run 12V stuff off the accessory socket.
Eastern Beaver has all kinds of SAE/accessory socket (Powerlet) cords and adapters. Very nice to work with and their shipping (cost and time) is very reasonable given where he is located. If the bike doesn't already have an accessory socket, I'd get the BMW one as the harness is already in place and it really is plug-n-play. Check my post in this thread for a few more details on what I did with my bike:
http://www.r1150r.org/board/viewtopic.php?f=2&t=14070
2) I don't bother covering it in the garage. I encourage my kids to climb all over the bikes: gotta start sometime getting them comfortable on the motorcycles! I do keep them on center stand and have taught the kids how to mount and dismount the bikes safely without damaging them. Every once and a while, I do find that the bike won't start because the kill switch is in the "off" position.

I do have a travel cover that seems to work pretty well, packs up small, and is inexpensive:
Nelson-Rigg UV-2000. I use it when the bike is parked outside all day in the FL sun when I'm at work or overnight at rallies, etc.
3) I usually don't use anything except the fork lock. I'm not sure what a wheel lock gets you that the fork lock doesn't. I personally don't think alarms are worth the time/hassle/annoyance, but that's just me.
4) I like the BMW fly screen. Large enough to get the air off your chest and small enough to keep your helmet in clean air (I'm 5'10"). I prefered it to the bike naked, and FAR prefered it to the BMW Sport screen.
I would most definitely get the metal quick disconnects. I installed the Omega ones which are very nice. However, I saw these at a rally, and they looked very interesting (supposedly, then can get both ends straight for you):
http://www.racerpartswholesale.com/cate ... isconnects. The advantage is that the o-rings are captive so there is no chance of damaging them and they are extremely easy to use. The downside is that they are not compatable with the OEM plastic ones. With the Omega ones, make sure to dab a tiny bit of silicone grease on the o-rings and be carefuly when releasing/connecting them so as not to damage the o-rings. I have removed my tank 4 times since I bought the bike 6 weeks ago (yes, that is excessive), but was REALLY glad I installed the QD's the first time I had it off. Removing the tank with metal QD's in place is absolutely nothing to be afraid of. If you're worried about it, a few extra o-rings on hand is not a bad idea (I took the old ones covered in silicone grease and put in a ziploc bag in the tail trunk).