The Chipmusic have two types of big limitations, one is the technical limitations of the soundchips (channels count, waveforms, effects, rom size, volume control, etc) and the other is the "game environment" limitation or "mental limitation". There's a very deep interrelation between those two factors.
The first is very well known so I will try to explain what the second one means and how it is affected by the first one:
The majority of chiptunes comes from actual games and the big majority were intended to be played as a background thing, as a secondary factor in the whole gameplay. This adds new barriers to the composers, and, back in the day, they were asked to make songs that:
1) Loop beautifully (lack of tempo changes fits here by 30%).
2) Doesn't distract too much the attention from the actual game (the lack of changes in the percussion tempo fits here by 60%)
3) One channel of your track (almost always the percussion) will be removed randomly from your song because of sound effects (this was very popular on chips with less than 6 channels)
4) The player routine code should be very small (for that reason you can hear very simple tracks in good games or very complex tracks in bad games, because of the rom space distribution balance, too much graphics but little music, too much levels but no music, too much music quality but no space for textures, and so on)
5) Your song should be very small too! (memory space!!!), for that reason the loop should be perfect, sweet and gentle (point 1)
6) The speed. Your music runs side by side with the AI, collision detection, rendering, etc. Maybe ALL of your songs were forced to run at 150bpm because of the scan cycle (update frame), or to be a factor of 100bmp who knows.
There are many more things to add to this list but I don't want to fill this post with technical stuff, the thing is that the Chipmusic is limited by many things and not only by the channel count and waveforms. Maybe you're thinking that you have found a new niche to exploit (tempo changes, crazy drum patterns, that's cool!), but the reasons behind why it is not so present is that the Chiptune have a soul molded since the cradle, that psychologically affects what you can do, and makes the excessive complexity in the final rom size or a tricky loop a good reason to get you fired...
Contemporary chiptune artits have all of this in mind, so think as a composer in the 80s writing assembly code and, suddenly, you will understand lot of things of the Chipmusic. It is a form of art not only limited to waveforms, it has part of the history inside it.