I LOVED G1 Springer and Octane. I played with and transformed them ALL the time!

Man, good times.

So I wouldn't lump Springer, Octane, or Cyclonus in with G1 Ironhide and Ratchet.
I have G1 Ironhide and Ratchet, but they are in SERIOUS played-with condition. But I didn't buy them, they were given to me. I wouldn't have bought them in the `80s, and I wouldn't buy them now.
So, yes, Ironhide and Ratchet need modern figures.
Now, I might get flamed for this, but I never liked the toy for G1 Megatron. Just ugly as heck. Galvatron was better, but still ugly.
G1 Sky Lynx, Ultra Magnus, Broadside, Gnaw, and, actually, the G1 Predacons, and, like you said, Runamuck and Runabout. Now, to be honest, I never cared enough about the *characters* of Sky Lynx, Broadside, Gnaw, G1 Predacons, or Runamuck & Runabout to actually care that their toys sucked, but even if I had cared about them as characters I still wouldn't have bought their toys.
Sky Lynx and Gnaw I just couldn't care less about; modern toys based on these characters would have to be freakin' amazing for me to buy.
However, even though I don't much care about Broadside, I do think its cool that he'll be getting a modern toy.
So, really, while most of the characters in the first 3 years of G1 would benefit from modern toys, there really aren't that many that I would never buy.