Hello, I've just finished mine and am waiting for a decision, so I know the position you are in. I wouldn't 'name drop' theorists unless you know they have direct relevence to your subject area and maybe chose a couple of juicy quotes from them that illustrate a point instead of just mentioning names. Also, I found that structure was really important, make it as tight and succinct as you can, and lay out the chapters very clearly. Try to draw some bold conclusions, it's hard because you don't know what you are going to find, but you can give some 'educated guesses' at what the research might yield.
Think of the proposal as a sales pitch, you are trying to convince a selector that this is a brilliant idea and that you are the best person to undertake it. Good Luck!