Hopefully Lance Henriksen will be back after cancelling last year to join Rolston and Goldstein.
Other suggestions would be getting Michael Biehn back and really would love Bill Paxton and any other Aliens cast (have met Jenette Goldstein, Ricco Ross, Michael Biehn and Daniel Cash so far......)
Obviously Sigourney, maybe try for London again as I missed her a couple of years ago.
Non Aliens people would be
Anyone from X Files
Wes Studi
Yvonne Strahovski
Judith Hoag