Can it be dirtied up a little?
I was thinking inserting TS like clipping and of course it would be switchable to stock design.
I'm not sure what adding clipping diodes to the wien stage would do. If it was a virtual ground amplifier sure, it's the same as hard clipping, and it probably won't oscillate because it didn't before and the diodes can only limit the gain. It might have some "unintended" effect on the whole operation of the stage though.
That said, I agree in putting the clipping in the first stage and making it adjustable, it's free to do that and it allows you to shape the result afterwards. Scaling the whole baxandall up by 10, adding a series resistor and shunt clipping could be interesting too, but there's the problem of having enough gain for the clipping without clipping the mid band eq.
also, putting the diodes across just lugs 2 and 3 of the pot, while there is a series resistor from the output of the opamp, will short the diodes out at minimum gain for a clean sound and soften the clipping slightly at higher gain. a neat trick, but i haven't seen it used that much.
that works, I think I've seen it somewhere, but a tiny bit of series resistance goes a long way with diodes, and it's hard to combine that with the large resistances needed for clipping gain. At that point the op-amp is probably clipping more than the diodes.