I think the Predalien is already alive when the movie starts because it kills off all the preds on the scout ship.
If the crash kills off everything save a Pred that can send out a distress signal, then that wouldn't be an issue. It would just mean that the PredAlien at the beginning might not be the same one we see later. We know that the Strause's have re-written the script, and the test tubes seem to infer that the Preds have a specific intention to create a controlled infestation like in the comics. Maybe this facehugger survives, implants the older male with a PredAlien embryo, and then we get another. The only messy thing I can think of is how Chet could create pure Aliens being a hybrid and all.
It'd explain a lot- why Chet is a Queen, as well as why it looks more like a crossbred Alien than the normal mostly-pure variety.
There's no webbing between the fingers,
I would implore you to click on the pic so as to magnify it and check again. I can clearly see brown membrane there covering our view of the hunter's flesh-toned skin on the left side of the pic.
no armour over the sacks, and it's nowhere near as large.
Two things- if it's a hybrid, it won't look the same; the second is that ADI is notorious for updating their designs after the fact.
Another EDIT: the hunter doesn't seem to be cocooned which would suggest there's an absence of an adult Alien, so perhaps this is like AVP in that it just bursts out once he comes to while still in the open woods.