Won't this just further encourage hybrid tanking since it will effectively push all weapons to near neutral damage on the off-type? You will literally never be significantly resistant to any damage type, but still weak to certain ones.

I would think the opposite would be true

Caldari currently running plates to stand a chance against lasers and Gallente scouts running extenders to avoid mass drivers/grenades

Why would you not play to your strengths, Caldari running shield regs in lows can quickly regain full health, running plates means enemies may have already closed the distance by the time your shield regeneration starts.

I'm sure some people will still do both, but this will benefit new players to learn the race doctrine and require less sp (don't have to get armour/shield modules both up to 5)

Except conversely, Caldari can laugh at Explosive weapons. Under your system, Caldari would not longer be resistant to explosive, meaning that they are basically weak or barely resistant against everything. That being said you would be encouraged to simply stack as much HP as possible because in all situations, you are never resistant to anything.

At least as Caldari you know that you'll be able to handle Explosive, Kinetic, and Rail well, in exchange you're very weak against 2 of the 5 profiles.

I guess personally would rather be super weak against 2-3 profiles and resistant to 2-3, instead of weak against 2-3 profiles and not resistant to 2-3.