Actually you are on the right track already. A small number of different fish with larger numbers of them usually ends up looking better than a big variety in small numbers. That is especially true if you had shoaling fish like black neons or rasboras, either of which would be fine with the angel / cory main stocking. It would be a good substitute for the swordtails if they are not one of your favorites. The black neons are big enough to avoid predation by the angel and do shoal to some extent.