In Belgium you can digitally sign documents with your e-ID (mandatory ID card issued by the government) and it has the same value as "classic" hand signed documents. I use it myself for everything, whenever I get a PDF I just sign it with my e-ID and send it along its way.
Why not make that your signature? Could you like, sign the current date with a private key, and write the result into the signature box?
That only works if the other party is capable of verifying it. Also how do you tie people to keys? Have the government issue them?
At bulksign.com we have this feature, it's called "Local Certificate" signature.