I don’t see how, though I understand the arguments in its favor. I can imagine a German leader saying to her citizens: “We need to pay this one-time clean-up cost, hold your nose and support it.” (Actually maybe I can’t imagine that, but that’s another story.) I cannot imagine such a leader saying “From here on in, we’re in the same boat with them.” The latter seems to be like too much affiliation for anyone’s comfort, and on the back Greek end the associated long-term fiscal restrictions would rankle to say the least.
Imagine that you had an insolvent relation of uncertain future creditworthiness. You could either make a one-time transfer of $10,000, to help pay off a debt, or co-sign a mortgage. Wouldn’t the latter be psychologically harder to do, even if it involved a smaller expected subsidy in real terms?