IMO, the rationale for intentionally introducing banana lily to your pond should be premised on your pond's depth-profile.
If the pond has a significant amount of shallow water (the term "shallow" is relative to water-clarity), I'd suggest a cautious approach - since banana lily may overtake any areas in which adequate sunlight reaches the bottom (as with most aquatic plant species).
Here's a classic example of a private lake that supports a healthy, yet relatively confined population of banana lily (photo-date Nov 5, 2012).
In the lake's two lower compartments, banana lily occupies most areas with water-depths less than 3'.
Based on personal experiences, once established (and largely due to it's tubers), banana lily can be challenging to manage. So, make sure your pond's depth-contours are conducive to naturally regulating the plant's proliferation before it is intentionally introduced.
