I think people hate those "teflon" capsules just because they don't sound anything like the old "brass" capsules.
I quite like the "teflons" (the linear version, that is) for what the C414 is really supposed to be: a utilty mic. It's not a magic bullet type of mic but a do-it-all mic. No, they don't have any special voodoo or mojo, but you'd be hard pressed for an application where they really suck.
Practical suggestions:
If you only need the cardioid setting, you could use the Oktava MK 012 circuit. It's a simple yet good sounding circuit, and it will do without a dc/dc converter for cardioid (and omni, if you want). Other patterns would require either a dc/dc converter (see C414 EB, the silver one) or intricate switching (see C414 EB P48, the black one).
You could buy an inexpensive multipattern mic with decent electronics and swap the capsule. My suggestions would be a Rode NT2-A or NT2000 or a Studio Projects B3.
I wouldn't go tube. I've tried a C12 "teflon", linear version, with a tube circuit, and it didn't thrill me. That's because the capsule istn't meant to thrill. So I think the "teflon" capsule, at least in the linear version, and a tube circit (which is meant to thrill) is a mismatch. May be different if you have the other "teflon" version with a treble boost as used in the C414 XL II and C12 VR.