This could work. The danios might get nippy with the betta so you might go with something a little more laid back. You need to be careful which tetra's you go with. Some are very docile and do well with bettas, other can be quite nippy. I would stay away from the gourami's. They are similar to the bettas about territory and this could quickly become tragic. I know you didn't mention them, but I would not do angels either. Just from my personal experience in my own tank I have found that the angel has been nipping on my betta. Nothing serious yet. Make sure you get the correct species of pleco so you don't end up with some giant on your hands.
I have a betta in my 55G community...see sig.... he is getting along very well(other than with the angel). Good luck.
One last note.....the success of this not only weighs on the fish you choose, but also the betta itself. There are some bettas that just will not tolerate any other fish. If this is the case with the betta you choose, make sure you have a backup plan to move him out quickly.
