Thanks for the suggestion. Actually, I thought about it, but didn't do it for a number of reasons:
1. It meant a little extra work, and I had already run out of free time at that time so I wanted to release it ASAP; and I was not sure if there'll be any interest in it! So, I decided to go without that feature.
2. As I said in the first post, you can abuse other OS icons for a few extra OS options (e.g. Using Ubuntu for booting another version of Nemo)
3. It is somewhat inconsistent with the current Ubiboot design, where each entry is dedicated to a single OS, and the extra menu provides only kernel selection. As in your example, such a feature allows adding an entry for Sailfish among Nemo entries!

But, as you said, it seems like a good addition. Specially, since ubiboot is currently lmited to 6 OSes, and with N9 Easy Boot you can easily have more OSes, I'll try to look into it at some point (Patches are welcome too!).