There will be a TMCC controlled whistle steam board coming, we haven't given up on that project. I was initially going to modify another little ERR board, but I'm thinking I may lay out a board specifically for the task. If I mod a board, I have to hand hack each one, if I build a board, I can produce them in greater quantities with a lot less work. The plan is to have an ouput for whistle steam and blowdown. Of course, I'd also include the enhanced chuffer and lighting effects on the same board so it would be an all-in-one.
I did do some software work on the whistle steam and blowdown, it's really the hardware that I need to create now.