You can indeed start MEP training before you have 70 hours P.1, as long as you have the required hours when you apply for the rating.
However, I think you'll find that some MEP training organisations actually use 70 hours P.1 as an entry requirement for the course. If this is laid down in their approved training manual there might not be a way around that.
Additionally I'd say that thinking about doing twin training with 10 hours P.1 under your belt might be regarded as a little bit overambitious.