As long as Twilight wont sit on throne away form her friends and waste her power and talents by ruling and doing paper work, I will gladdy welcome Twilight as Alicorn.
Being Alicorn does not mean she will become all powerful, it just mean that she can train her magic to become even stronger, she can learn to fly, train her strength and endurance, something she can do with her friends and then use to protect them when another crisis show up.
They must, they must they must reprise "I Wasn't Prepared For This" when Twilight transforms! It would make a wonderful bookend for the season. It has been, after all, the season where the unexpected has happened - Twilight learnt that magic wasn't enough, Rainbow Dash quit the Wonderbolts rather than protect a hotheaded trouble-maker and Pinkie Pie learnt that too much fun is a bad thing.
Now this has happened, the ultimate unanticipated consequences to her path.