You have formulated your Big Idea. It helps you to both structure your presentation and prepare answers to potential questions. We like to add two components to the strategy: the biggest strength and the biggest weakness.
Strength
In the next step you will brainstorm about your unique selling points. However, one of them sticks out. It is the one usp that rules them all. If you could choose one reason to give you the money it is this one. It can be a dataset that no one has access to but you, your outstanding CV, proof of principle that you published after the submission of the proposal.
Choosing such a strength, helps you to give it a prominent place in your presentation. For instance, if you have a unique CV, you might tell the origin of your story as the beginning of your presentation. A unique collection could be the center piece of a methodology slide.
Weakness
Perfect projects do not exist. Each project has its weaknesses. ERC projects are high-risk, high-gain by definition, so feasability often could be perceived as a weakness. Or, projects heavily resting on previous work, might seem not ambitious enough.
We advice to determine the most obvious weakness in this stage of the preparation. What is the question that you fear the most? Of course you should prepare an answer for it. However, it is even better to pro-actively work with it in your presentation. Do not call it a weakness or a risk that needs mitigation, but reframe it in such a way that it is much less of an issue. Or it might even be a plus.
For instance, if you have chosen a host that does not have a group in your field yet, it might seem to be a waekness. You might explain how you overcome this obstacle. However, you might as well link it to the ambition of the project. This place allows you to start a new group around your idea and build it from the ground up. Or, you have a relative underdeveloped CV for this stage of the career. It can be a weakness that you hope for they will not notice. At the same time, it might also be the result of a non-standard career path in which you where involved in pioneering fieldwork that consumed a lot of time, but that brought you into the position to execute this unique project.
Ignoring the elephant in the room is never a good idea. Counter it with a proper frame in your presentation, and prepare yourself for questions about it.