you want to build up a dynamo-hub with 27" wheels? did I read that right?

I wouldnt bother with a bottle dynamo -- not bright enough, in my opinion, and the drag would drive me nuts.

I'd say my top priorities would be a quality wheelset & wide tires -- at least 32mm in 700c. I'd just save up a little more and get 700c and some good tires (rivendell jack browns, vittoria hypers, schwalbe kojaks, etc.). 27" to 700c will provide extra clearance...and wider tires means more comfort, low psi, more terrain that can be ridden, and no more swerving around cracks in the pavement. Quality handbuilt wheels are an essential upgrade for any cyclist. Pick up some tektro long reach brakes as well.

If you're planning on doing randonneuring events or centuries, I'd also recommend a handlebar & saddle that you find comfortable over many hours and miles.

as for bags, I think acorn is making the best affordable bags. I also recommend swift industries and loyal designs. of course, berthoud and inujirushi are excellent as well.

http://www.acornbags.com/
http://loyalbags.com/
http://www.builtbyswift.com/

if your fork doesnt have cantilever posts, invest in a nitto mark's rack: http://www.rivbike.com/product-p/r1.htm or consider this bag: http://www.rivbike.com/product-p/bavbb.htm

But perhaps your bike might work better with a rear load -- front loading isnt for every bicycle. consider a rear rack instead (and panniers or trunkbag) or a saddlebag. I'd just get a quality saddlebag like a carradice and a bagman for support. That might be the best bang for your buck -- lighter, more carrying-volume, less expensive than buying bag/rack, and no p-clamps on the fork legs. and then get a small handlebar bag for food, etc: http://www.rivbike.com/product-p/bavbt.htm ...or some jersey pockets.