It'd be very easy to put in a series/parallel switch, and relatively easy to put in a coil tap style switch in.
Ther are loads of electronic gizmos out there, built in OD/Distortions or EQ's and stuff.
Have a look on
http://www.axesrus.co.uk for some of the pre-built stuff.
http://www.diyguitarist.com has some cool stuff on it too.