You're right, you can look at MA that way. Personally I view the current trend of competitive sport fighting that way! And I have to also add that everything there, bar certain 'terms' are within the Wing Chun I have been exposed to. Albeit my groundwork was 'self studied' with what I had learnt and discussed with some pretty well know BJJ players to make sure I wasn't just coming to the wrong conclusions!
So to satisfy what you think consitutes Martial Arts, or the building blocks at least, I don't need to crosstrain or evolve my Wing Chun.
What constitutes MY Wing Chun Martial Art understanding?
1. Form
2. Interaction
3. Equipment
4. Weaponry
5. Literature
Now THAT imhhho is a complete Martial Art