Imagine a sessile, multi-cellular slime like organism (or whatever necessary) awaits in a burrow or along a tree branch. Then an animal lands in its ooze and is trapped and soon paralyzed by its venom like secretions. Then the shapeshifter envelops the creature, digesting it completely and obtaining the prey's DNA through horizontal gene transfer. It then creates a womb-like cocoon, creating either a clone of the original creature, or its body, and uses this more mobile form to spread itself across the environment. Is this method of reproduction feasible, and what problems would the shapeshifter encounter?
Edit: The shapeshifter would reproduce itself asexually by regurgitating part of itself into a suitable location.
(I know there are simpler ways to accomplish this, but I felt this was an approach towards shapeshifting I haven't seen before)