There is many things that Captain Sim can do.   Lots of different aircraft however; I'd be really interested in and update to the CS-130X as it was discussed in 2008.

The once talked about KC-135 addon for the 707 variant would be really nice.  

Working on the KC767 addition to make it work accurate would be a huge plus.

I own just about everything CS makes with exception to the L1011.  Once they finish that to an decent version and the 9.99 sale happens it will be in my collection as well.  

Just humble opinion from a simmer

Don