You might be right there actually.
EDIT
Here we go (I don't know when Mike wrote this, but Anchorpoint has been offline a long time now)
QuoteThe Development Theory
The current, and most widely accepted theory, suggests that the use of the tube-like mouth parts may not be for the depositing of an embryo in the chest of the potential host organism, but possibly a means of regulating TTXIR which renders the host unconscious and the introduction of a viral agent - which would then make the host body responsible for the creation of an embryo in much the same fashion that an organ may be produced through the creation and designation/specialization of various cells, via restructured genetic coding. Under such an idea it is easily seen how an Alien embryo would be able to adapt to varying host organisms, and vise versa. This idea would also better explain the positioning of the embryo in the host's mediastinum, when the Facehugger's mouthparts are known to only extend part way down the host's esophagus.
The use of the host's esophagus is still vital to the play of this particular theory. The esophagus' lining is a mucus membrane, which would greatly aid in the transmission of genetic material. Once the DNA restructuring material has successfully altered the host's genetic code the host body would then begin the development and growth of the I. raptus embryo as if it were part of its own physiology. In effect the host organism's body is being told to create the embryo in the "free area" of the chest by it's own modified DNA. An additional benefit to altering a host's DNA so as to plant an embryo is there would be no rejection of the embryo as it is now seen as part of the host organism's natural structure. For more information on this please see the DNA Reflex essay.