EPQ ideas-

You have to pick something you're willing to use (waste) a lot of your freedom for this project. It is extremely long and sometimes tedious. Depending on your board, many of the marks may not even be related to the content of your project. However, the satisfaction of finishing the product is great.
In the relation to specific topic, history at A level often creates quite restrictive questions so probably try something completely different in terms of the question itself. And don't make the question too broad, that was the biggest thing I took from the EPQ, keep the topic focused.
Some questions could be:
To what extent has the Slave trade defined global politics?
Which world war was of greater impact? (with this question you need to decide impact on what e.g.impact on economy, international relations or something else)