Suggestion about research plan
As much as anything, the purpose of the research proposal (in the UK at least) is to show potential supervisers that you have the ability to construct and justify academic research, can write clearly and put forward coherent arguments. It is unlikely that you would be held to the specifics of your proposal. Once you have been accepted somewhere, it is generally accepted that the details of your research will (at least) be refined, if not completely changed! Just think of it as a way of demonstrating your abilities.