To summarise...
There is no way to what you want with the current tagnavi implementation.
Solution:
Submit a clearly worded feature request to the Flyspray tracker system and hope for the best.
Workarounds:
Re-tag files as discussed above.
Completely miss the album step and display everything as a flat song structure per artist, i.e.,
Artist>
     Linkin Park
- Track 1 (Hybrid Theory)
- Track 2 (Hybrid Theory)
- Track 3 (Hybrid Theory)
- Track 4 (Hybrid Theory)
- etc
- Track 1 (Meteora)
- Track 2 (Meteora)
- Track 3 (Meteora)
- Track 4 (Meteora)
-etc
- Qwerty (Live)
-Track x (< untagged >)
-Track y (< untagged >)
    Metallica
-etc