Been reading this thread for some time now. Many interesting arguments here, and in agreement with certain number of posters, I too feel like it is virtually impossible to make hull and shield tanks equally viable. Outside of what already been posted, the system just doesn't support it. Current implementation of shields is way too convenient, and to fix this, it would take one big re-wire of whole system to be much less beneficial and introduce more micro management.
As perfect example of hull to shield balance interaction would be a small game named Starsector. When you have shield on, which can be configured into front/omni or full, it generates flux (or heat, translating to Elite). Depending on flux profile of the ship and ammunition type used against it. Constant pressure can build flux up fast, which renders ship inoperable in certain terms, much like fully drained distributor in Elite. And unless you find a way to naturally dissipate or vent flux, you will have limited capabilities for offense and defense both.
Regarding hull, it is possible to create multi-layered setup. You have to crack armor first before you get to hull itself, which can be quite tough and all modules disabled from damage (which can also cause flameouts) get auto-repaired, or rather re-booted back in combat state, which depends on specific mods installed in the ship and how badly vessel is damaged overall (along with Combat Readiness stat, which is different story). But with a twist, that hardpoints don't really use set "health pool", so its not as easy as in Elite to destroy this systems. There are few other details, but long story short, with that system, shieldless ships are fully viable and are on similar footing as shielded ones, where certain frames can do either better.
It is unrealistic to assume system Elite is built upon will be completely scrapped and replaced, so guess we're stuck with what we have now. Drastic changes to it might actually be harmful, even...