Illustrator today allows to make Enclosed Selection Mode a permanent option, with with the Select Objects only within Marquee option, in Preferences > Selection & Anchor Display, as was requested here and in a separate request at http://illustrator.uservoice.com/forums/333657/suggestions/49503929

But I still can’t use it fully today.
I isolate often, and Selection tool does not allow to use Enclosed mode when isolated. For some strange reason it requires the Group Selection tool to do so, as if my scope stays at the document level, and I’m no in isolation! Make Selection tool work in Enclosed mode in isolation, please.