class User
  has_many :group_roles
  has_many :groups, :through=>:group_roles
end

class GroupRole
  belongs_to :user
  belongs_to :group
end

class Group
  has_many :group_roles
  has_many :users, :through=>:group_roles
end

group_arel = Group.where(:active=>true).where(:important=>'very')
groups = group_arel.to_a # returns [group, group, group]

user_sql = group_arel.joins(:users).select("users.*").to_sql
User.find_by_sql(user_sql) # return [user, user, user] for all the users of all the groups on #17

# What I'd like to be able to do
user_arel = User.take_everything_but_the_select_from(group_arel)
amended_user_arel = user_arel.where(:name=>"bob")
amended_user_arel.to_a # returns [user, user, user]