Sounds like a good plan
Altos aren't supposed to be that good with the shellies the altos are supposed to get big enough to eat the shellies.. I can't see it being an issue with the altos I have at the moment and I think Smidey has them together with no issues.. Plus I don't know if you would source any altos anyway they all seem to be being snapped up and kept quiet..
Tropheus would be awesome, and go well with the other 2 suggested. Dubs are a good choice they are nice looking and cheap enough to get a good colony going. I would probably go with pemba or firefox, the bulus are pretty agro and would probably dominate the dubs pretty easily and also (IMO of course) the bulus are nowhere near as colourful, it really depends on what you like.