It doesn't make a difference to me what you end up doing, but I think your missing what I'm saying about power being equal. A transformer simply transfers power, it doesn't increase or reduce it. It changes the voltage/current relationship. The amperage is going to be the same through your disconnect regardless of whether you keep the transformer or ditch it. Because the voltage through the disconnect is not changing and the power required is not changing the current is not changing. The previous system only seen a reduction in current on the secondary side of the transformer, which is the controller side. This is why the data tag on a dual voltage motor has 2 amp ratings and 2 voltage ratings but only one HP rating. I'm speaking of Power in the electrical meaning of the word.

Keeping the transformer wouldn't hurt anything, but it is unnecessary. Unless you want to keep it for helping reduce harmonics. But if alpha is supplying a line reactor in the controller(they should be), that is sufficient.