LOL!! That's a good one.
I think that having the ability to specify lens filters would be great, polarizer included. Filters and gels could be like MXMs and fully editable by the user and we could build up a library.
With glare you can accomplish some effects and most everything else can be done in post but that defeats the purpose.
There are a lot of effects that can be done at the lens that would be useful. Like a split focus filter for example.
Lens modeling and filters would be good, but please get the plug-ins working right first.
D