Alright matey, I've only got a 15" Powerbook so might not be able to comment on a few of those performance questions you've asked.
However I do find that size could be a bit of an issue especially if you're going to be treating the machine as a portable warrior. By the sounds of things you'll be carrying your MBP around for quite a fair bit so the bigger it is the more weight/space it will take up. Especially you'll be taking it around to tune ECU's and so forth do you really think you can justify the extra price and weight for that little extra screen real estate when you don't need it?
My personal point of view is to get something as small as possible if your intending to use a notebook for its primarily purpose (to be taken around). You'll thank yourself later when you have a million other things to carry with you.
If you really must have a 7200rpm SATA drive in a 15" just get a certified mac tech to fit one in for you, depending on your location there's quite a few of them floating around here somewhere that would be more than happy to assist you.
Temperature wise my G4 gets bloody hot, to the point where is unbearable to be used on my lap if its a 30c plus day. Your millage may vary on the intel chips but I wouldn't bank on that too much.
Just to give you a rough idea of the CPU temp on a 22c day. bottom of my CPU reads 50c and power supply is at a whopping 55c. I'd sit that on my lap just not for extended period of time.
Wireless side of things the MBP is running on 54Mbit (802.11g) only. Although I'm not 100% sure there might be a software update to get it up to 108Mbit? The range has slightly improved from the powerbooks as far as I can see, but its still a little disappointing as most PC's with a built in chip will generally out perform our range. Once again personal experience.
You might have to talk to a few expert bootcamp users to find out more about the driver issues, if possible try to find a local member in your area that is happy to test those softwares out for you. Frying an ECU is no fun, as reliable as mac's are in general I still wouldn't trust it with windows installed...
Last but not least, get as much ram as you can afford! You'll thank yourself later!
Thats my 2c worth at 10am in the morning, hope I haven't rant on too much...
