The Dia Compe levers with the centre pulls will be a good combination, and so with the campag ergos with the Tektro DPs. With ST4700 you must use a NSSLR caliper, else older DPs will be a 'bit wooden' and centre pulls will be quite a bit worse than that.
You don't need a calculator to see that altering the straddle length doesn't make that much difference with most CP brakes; obviously the caliper MA reduces whenever the brake blocks are lowered in the slots, but at the straddle end, just put a horizontal construction line through the two arm pivots, and see where the projection of the straddle cable intercepts them. From the intercept point to the arm pivot is the 'virtual arm length'. If you can make this arm length longer, then the MA is improved. However whilst you can improve matters, IME you never get that much bang for your buck by altering the straddle length (mainly because the straddle is always anchored close to the construction line) and what you do get is usually lost very quickly as the brake blocks wear, if you adjust the cable in the normal way.
The only cantis which respond well to attempt to tune the MA are mid-arm ones; it is the same story with virtual arm length but in this case you can soon work out that you can roughly double this between a very poor setup and a very good one.
cheers