rewire older speaker internal wiring?

besides upgrading the wire, why not look into updating the crossovers also ?

I'm also with Riley. I re-wired my existing speakers with Vampire wire from The Cable Company which I'm sure helped but the greatest improvement was replacing my capacitors with Duelunds VSF.
If you can afford it the Duelund Cast capacitors are supposedly even better?

Capacitor choices are near-limitless!
From Russian military to fragile bees wax you can spend anywhere from a few bucks for say... Solon all the way up to Stratospheric for Jensen or Mundorf or ??

Set a budget for how much you think it's worth, and how long you intend to keep the speakers. They ain't getting any younger!

If you intend to keep them forever and be buried in the box they came in, spend whatever it takes. Any inductors and resistors can be replaced at the same time with audiophile grade parts.
Check Parts Express or Madisound and come up with a plan.

I am currently working on such plans for my panels, doing a rebuild of the STOCK x-over in my 1.6 maggies. Many choices, not the least of which is that I will probably end up with an external x-over since the proposed cap upgrade (Clarity SA) and new inductor (aircore) take up LOTS more space.