will this work?

Greetings cat friends -- I lost one of my two formerly feral cats to a
speeding car last night, and I am now considering building an outdoor
enclosure for the other. Is this realistic? Can ferals live happily
in enclosures? She has become quite tame, but she is very much used
to being able to roam about at will, and becomes really agitated when
she is restricted at all (such as on our screened porch or if we let
her in the house). There is simply no way she will ever be happy as
an indoor cat, but I can't bear the thought of losing her too, since
I've become so attached to her. Could she have a happy life living on
our screened porch? We could put up stronger screen and a latching
door so she couldn't get out, but I'm afraid that it would not be a
good quality of life for her. Any thoughts? Thanks -- M9