There used to be an option in Windows XP called wpa-none. It used the preshared key for encryption, so this isn't a secure option. Perhaps using hotplugging so if you lose the link on one AP it can authenticates with another.
This link may give you a starting point. You should put your distribution in your usercp so we don't have to make assumptions or be overly general in our answers.
Look in the wpa_supplicant's sample configuration file.
Read the description for "apscan=2" option.