Reducing the number of expensive capacitors in an audio opamp circuit
Ok, firstly I think that switching circuit is going to click, no matter how many caps you scatter around, simple charge injection in the cmos switches will see to that at the impedance levels you are running there. 

The trick with coupling (as opposed to filter) caps is to keep the AC voltage across em negligible, which is to say make them large compared to circuit impedance. So long as you keep the AC across the cap below 80mV or so the distortion is negligible, and as you know the DC conditions on your caps (4.5V give or take) there is no problem just going with 10V, 22uF electrolytics here, they will not be a problem and are far cheaper then messing around with PP or PPS film.
A further note, your output cap is 2.2uF into 10k, which sets the LF rolloff, your input caps do not need to be sized to roll off at a frequency 1/30th of this, so maybe you can downsize them? Bit of luck, C0G ceramic may not be out of the question.  

My first thought were I doing this thing would be lose the analog switch and go for a couple of jfets instead, use a dual opamp so you can buffer to get the impedance down to something sane, couple of jfets to do the audio switching (Probably need to pick parts with low pinchoff voltage as you only have 4.5V to play with).

The trouble with just floating the whole thing 4.5V above battery negative (which is sort of tempting) is that looking at that board you have an external DC input, and many pedalboard supplies make a nasty assumption that it is ok to connect all the negative rails together.