Thoughts on Common Emitter Gain Stages, Feedback Caps, and Impedance.

[Bill Mountain]

I was doing some thinking about the Big Muff input stage.  I love this little circuit and I'm thinking of using it as the input stage of a dirt box I'm working on.
The only thing that bothers me is that it has a low-ish input impedance which helps it smooth out the highs when the guitar is plugged straight in but since it will always sit after my tuner pedal it can sometimes be brighter than I want.

At first I was doing some thinking about ways to raise the input impedance so it would sound the same whether it was behind a buffered pedal or not but then I had this thought:

Is it possible to select a feedback cap that will tame the highs with a buffered signal the same way the low impedance does with a passive instrument?  And if this is possible, would it sound the same with a passive instrument?

I've experimented with larger caps in the past (680p to 2.2n) and all it usually does is make it sound darker.

Have I just not found the magic cap value yet or is the high frequency roll off I'm looking for not attainable with a simple feedback cap?

Thoughts?