I am making this little test.
Download the explorer suite here
http://www.ntcore.com/exsuite.php
then open the Rebellion.exe (make a backup copy first) with CFF explorer.
go to "Nt Headers"
go to "File Header"
select "Characteristics" line, click on "click here" and select "app can handle >2gb address space".
Save and overwrite.
I think memory is increased only up to 4gb. but it should still be a great help for those huge mods out there like "Sins of a Galactic Empire".