My question involves guardianship in the State of: NY

Supposing a young child has been in foster care for quite some time, and the foster agency is recommending the child be returned to the mother...but the mother and foster parents are in agreement that some type of parenting arrangement shared among them would be in the child's best interest. Supposing the mother does not want to terminate her parental rights but would like to have some type of shared custody going forward with the foster parents.

Is it correct to assume that, once the child is no longer in care, the foster parents would have to obtain guardianship (or co-guardianship?) in order to continue serving in a parental role with the child? What do parental rights mean in a situation in which another couple also has guardianship?

In what ways could such a situation could be approached (any other routes in terms of joint custody?), and what are the pros and cons of each?

Thanks in advance...