What should I add to this custom amp?

[thehoj]

I'm all for leaving a good amp alone.. The only problem is that this amp I put together, which takes bits from the magnatone 213 and fender 5e3 (along with some other things I like), has an open spot on the front for a switch or pot.. I feel like I need to put something in there just for appearances sake.. And I feel like there must be something I could add that would give the amp a bit more versatility.

Here's a schematic:
http://s15.postimg.org/im2tjzcnd/Bogen_Conversion.jpg

The Tone control is very different to anything I've used before, but it gives me a ton of tonal range. The amp as also quite low power so I have no need for a master volume..

Any ideas on what I could add as a switchable or potentiometer based control?

[R.G.]

Why don't you put a 9Vdc output jack on it?

[thehoj]

Why don't you put a 9Vdc output jack on it?

I'm not sure what I'd do with that.. Are you thing for pedal power or something like that?

[R.G.]

Yes. It's a very rare amp that doesn't get used with some kind of pedal. Having 9Vdc coming out of the amp just makes pedal use easier.

I'm not sure why - except history - modern amps don't have 9Vdc out of all amps.

[g1]

Which polarity?