I was looking at the cross frame because it would handle disc brakes. It also has the braze-ons for fenders and racks. After doing the math even with used parts I quickly realized I was at the price I could get a Novara Buzz after the 20% off deals that REI offers.
The road frame does not have the braze-ons It is a Road bike first. So if you want a rack you are goign to need a post or use ugly p-clips to get it to work. Thats where I see a problem with that frame. If you are good with traveling light then go for it.
Personally If you have a active CL in your area I'd be watching for a C-Dale or newer Trek as a starting point. What you replace you can always e-bay the old parts you didn't use. You should be able to get a decent complete bike for close to $200 and you will probably get decent wheels and decent derailleurs for that price. STI equiped bikes you can find for $300 from time to time.
For Commuting I'd also consider going with a Sport (or Touring) over race (the Nash frame is a race/crit geometry). Sport frames will usually have a bit long chain stay and braze ons for fender and most of the time for a rack. I also would not rule out vintage steel frames. When running thin tires a steel frame really does smooth out the ride. You get into larger tires like 32's the aluminum is not that harsh. 700x23..it is going to buzz. I have two very simular bikes and have 700x28 on one and 700x35 on the other and the ride is dramatically different.
I have built two bikes up in the same way you are talking about and came up with great bikes for under $500 both times.
My one C-dale T700 I picked up for $220 and picked up Tiagra 9speed brifters, Octalink cranks, SRam gears and 105 derailleurs for $140. I ride the hell out of that bike and it is now basically the same as a C-Dale Touring II that goes for $1400. (it now wears the 105's and 700x28's and is my summer good weather bike)
My second T700 I picked up for $330 but it came with 8 Speed RSX brifters that I used on another project and I again found 9 speed brifters for $120 that came with the 105 Derailleurs. (now has the Tiagras and 700x35 more the bad weather with fenders and racks for winter) All CL finds.
You can do it on the cheap but it will take time.