aj on the LN IRC channel suggested an improvement to this technique -- a better way for Bob to pay Alice instead of using a one way payment channel:
rather than opening a whole new channel, why not send a "Bob pays 2.5 BTC to "Alice_Sig + BobSecret | Bob_Sig + TIMEOUT" and ask Alice to setup an on-channel payment to Bob of 2.5 BTC given BobSecret. Bob reveals BobSecret on the channel, Alice uses BobSecret to claim the on-blockchain 2.5BTC, everyone's square.
I also updated the original post to note that this does require BIP 62.