There are various genital packages for V4 that include a morphable anus - e.g. GSpot and V4WWG IIRC. If you need a male figure with that functionality, maybe you could make do with one of those and the V4 male morph and Mike's native genital  or the one from Satanica. 

Having said that, the anuses aren't that great as far as 'receptivity' goes if that is the aim (and why have it morphable if not).You might be able to fit a thumb in at full dilation but that's about it. I'm just guessing though, I haven't tried it. I think Have's Eroko figure is the only one I've seen whose anal and vaginal morphs would accommodate a significant amount of intromission (or expulsion), but she was built from the ground up. Anyone wanting to create a realistic depiction of childbirth* with Poser is out of luck without a completely custom model.

• Not to mention various unspeakable acts which I am told can be found on teh internets.

 

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken