I agree with everyone who has suggested that the best reason to go with an FE is to maintain a sense of tradition (esp. if you are completing an aluminum CSX6xxx car), or if you are planning a no holds barred, crazy-big stroker displacement...
But if performance/weight balance/handling/cost/etc are your primary design concerns, then you can build a better performing, more weight-efficient powertrain using more modern (and lightweight) design baselines...
Funny, but one of the personal aesthetic issues I still have with my own car (yes, the door leading edges bug me too, but that is
another issue
)
I don't like the 5.0 style intake on my engine, so I've been pricing out options to either change the induction to a carb-style throttle body, or maybe just pull this engine completely, and put in another... Because if I'm going to re-do the induction and re-tune, then I might as well do heads and cam, and if I'm going to do induction, heads/cam and re-tune, then I might as well swap the whole engine.
and if I'm going to swap the whole engine, then I have to decide on displacement...
But whatever I decide, I know it won't be a big block (neither FE nor 385 series), because it just doesn't need to be. I can do a 427 Windsor that's every bit as powerful as a 427FE or 428CJ, that weighs almost 200 fewer pounds to boot.
so, I guess my post doesn't answer your question about regret, but someday, when an aluminum Shelby continuation car drops out of the sky,
THAT's the day that I'll be going Edsel-shopping, and on that day I'll have no regrets about putting an FE into a continuation series car, regardless of how heavy it is....
But until that day, I see no reason to consider anything but a Windsor engine.