Connect your Ki with the Ki of you partner. You can do that with Aiki weapons, no doubt.
I have to ask, what possible benefit is there training to "connect (harmonize) my ki with that of my partner (opponent)" in weapons? Perhaps I'm being too simplistic, but the way I see it, an attacker with a sword would never want to "harmonize" their ki with me or create/maintain that sort of connection -- they simply want to defeat me -- so what are the benefits of both partners training to harmonize their ki? I think a better training paradigm is to have one partner deliver a realistic attack and have the other partner deal with it using his/her ki (and aiki) to control or defeat the attack.