Multiple, conccurrent authentication for WP & multi-sites?

Hi – does anyone know if WP in multi-site mode can be used to authenticate from multiple locations for different blogs/sites? My organization has an install with around 5 separate blogs/sites.

We use the muldap plugin to hit an LDAP server for all of the blogs to authenticate users for posts and for admin logs, etc. However we 2 new blogs/sites that want to use the WP internal method for authentication – is that possible to change authentication method on a per-blog or per-site basis? If so, how?

And also, is it possible for WP to hit multiple authentication servers concurrently? That is, can a user log in, and WP will attempt to auth from one datasource; if that user’s credentials are not found in that datasource, can WP then automatically move to another datasource and try that for login, and so forth, until it runs out of defined datasources? I’ve looked and looked, abut cannot find the answers to these questions.

thanks!