Well, here's what I have since come up with (I used to be Dr. Dementos) after researching other's ideas and concocting my own.
First, I like the Mega-Damage = +7 DCs idea, that is the best approach.
Second, based on that, you can then make equivalent DEF based on MDC
Just use the HERO's geometric scale for comparison
A character with, say, 100 MDC is equivalent to having enough defense to defend against an average 7DC attack = 7 DEF
This also means that any given MDC creature or structure should have 7 DEF in addition to their other defenses
So let's take that Glitterboy for example.
Glitterboy Main Body = 770 MDC
2^9.5 = 724
3 Active Points to 2 DEF for every 5 Active Points to 1 Damage Class (3/5)
9.5 x 3 = 28.5 Active Points / 1.5 = 19 DEF + 7 DEF = 26 DEF.
So maybe Rifts is not so powerful, just imbalanced.
We all have super-characters that can take this guy.
But what about his Boom Gun?
If memory serves me correctly, that is 3d6x10 MDC
This is my personal preference for damage conversion, but it has its kinks:
I take the type of die of damage that an attack does, divide by 2 to simulate the standard effect. This damage must be assumed to be BODY damage. That remaining number is the equivalent # of Damage Classes.
So back to the Boom Gun:
3d6, using these rules = 9 DCs
x10 has already been established as = +3 DCs
MDC = x100 = +7 DCs
9 DCs +3 DCs +7 DCs = 19 DCs = 19d6 Normal Damage or 6d6+1 Killing Damage.
There's your Boom Gun Damage.
And the rest is relatively easy to convert.
Sometime later I'll post about how I have decided to go about converting OCCs and RCCs.