Yes, I think that would be great. As I mentioned in the original post, we have a lot of customers that expect/need a more formal receipt for the transactions that they can save, print and give to accounting.
I'm not sure if I understand how you'd implement it, but here are some suggestions to take or leave:
The customer obviously needs the receipt, but I think it could be useful for the seller too. Perhaps there is a way for the seller to access all receipts so we can provide them to sellers after the purchase, if asked.
I think the Thank You page is a good place to offer the receipt, but I'd also suggest having a link in the email they receive after the purchase. This way they can access it later without trying to get back to the thank you page.
I've seen some versions of these automated receipts that also include a handy link to download the seller's W-9 form for tax purposes (another thing our business customers ask about). It would require an e-junkie interface for uploading the file, etc.
Of course it's up to you, but I think downloadable receipts are a feature that could be an asset for users like me. Cheers!