Bi-wire cables with non bi-wireable speakers?

Yes. Take care that the speaker binding posts can be tightened enough to maintain their hold onto a double set of your cable terminations, such as two spades per post, rather than the traditional single spade per post.
The use of Caig ProGold to prepare the cable terminations to transmit signal, plus Silclear from Mapleshade to enhance signal transmission should make for getting all the signal quality from your cables.
Also, check with Signal Cable to get their opinion about how to do it.

Yes, agree... If you can get a good hold on the double spades on one binding post, don't worry about it.