Don't anybody raise their Liver Fire too much over this, but here's a tiny bit of logical analysis of the ideas involved in this here discussion. :P
As I see it, there is an argument brewing between the proverbial apples and oranges. On one hand, we are discussing the value and merits of the ability to fight. This idea holds regardless of the style of fighting being considered, since it serves the greater priority of self-preservation.
On the other, we are discussing the value and merits of being able to correctly manifest the principles of a given internal art through physical motion, whether in combat or not. This also serves a greater priority; namely, that one ought to be able to manifest these principles correctly, to whatever degree, if one is to be able to maintain intellectual honesty in claiming to be an internal martial artist of whatever arbitrary level of skill.
The problems inherent in the discussion so far seem to stem from inconsistent and agreed-upon recognition of these two factors. There are three general ways to view the situation. 1) these are two valid but entirely separate considerations altogether, 2) they are not separate at all, but are in fact completely mutually defining for internal artists, and 3) they are able to be considered separately, but contain a certain degree of interdependence. Let me put forth a typical hypothetical argument for each of these for illustration.
1) "This is the correct choice because one can be a highly skilled fighter yet not be able to manifest internal principles well at all. Conversely, one may be able to correctly demonstrate all of the internal principles, yet not be able to fight well at all." This model implicates still other factors that may be involved in being able to fight successfully than those found in the Classics (which I am assuming to be the agreed-upon standard of internal principles, lest we open up an entirely new avenue for debate). This model further allows for the separate prioritization of fighting skill and ability to manifest internal principles correctly.
2) "This is the correct choice because, as internal artists, if we can't manifest the internal principles correctly, we will be unable to fight well, since the structure which provides so much of our power is included in the principles. Therefore, bad manifestation = bad structure = poor ability to fight using internal styles. Likewise, if we are unable to fight using internal skills, then we cannot claim to be correctly manifesting the principles; we are merely going through the motions. This shows that fighting skill as an internal artist and ability to correctly manifest the internal principles are mutually interdependent, and to some degree, probably even mutually defining." The major difference between this model and #1 is in how one is defining the ability to manifest the internal principles correctly. This model carries with it the inherent assumption that correct manifestation must include the ability to apply it successfully in combat since these arts were originally designed for combat purposes, in contrast with various similar qigongs which were designed with health as the primary purpose.
3) "This is the correct choice because, while fighting ability and the ability to manifest principles do contain areas of overlap, they are still separate abilities to a degree. That is, while it is true that an internal artist who can demonstrate principles but can't fight isn't really a complete internal artist at all, and likewise for someone who can fight well but can't manifest the principles, there are still factors that these two skill sets don't share. For example, timing and physical conditioning, while essential for fighting ability, are almost unnecessary for the ability to correctly demonstrate and physically manifest the internal principles. Likewise, while the ability to sense, control, and transmute the different qi's from the seven gates is essential to correctly manifesting the internal aspects at advanced levels in order to move beyond the merely outward manifestation, this ability has almost no bearing whatsoever on the outcome of a real fight." This model sees the situation as two skill sets which, at some point, dovetail with one another for internal artists. It does not contain inherent assumptions regarding the prioritization of fighting skill vs. ability to correctly manifest internal principles according to the Classics.
Which model is correct? I suppose it depends on how we as individuals define things. Do we recognize fighting skill and ability to manifest principles as two different concepts, as one in the same thing, or as some combination of both? If we view them, to whatever degree, as separate, which is given the greater priority? These are questions I believe must be asked by each practitioner at some point along his or her path as an internal artist. The answers are intimate, personal and may profoundly affect our practice of our given art and perhaps even our very lives should we ever find ourselves in a real physical assault. Whichever choice one makes, knowing why one believes the way one does is the only way to be congruent about the choice and avoid internal conflict over it.