Between the iPad and the iPad mini, there isn’t a problem with the size of your tablet getting in the way of performances. I believe the mini version finds itself a little sweet spot between a full sized tablet and a smartphone which can run the same type of apps. Where the tablet will succeed is in screen space and visual feedback that does not need to be negotiated or compromised to get full performance out of your app. The only real issue standing in the way is how the user intends to use the machine within their setup. Will they use it only as a visual feedback display? By not having to even touch the unit, you alleviate the latency and accuracy issues associated with many touch screen devices.
It could be used to analyze real time wave forms and EQ screens on the fly. But most will prefer to become much more proactive in their usage – opting to add some form of input to their tablet. Still, there amount of input a user decides to use should be limited and not be the central part of their performance. Using the tablet as a “remote” is a brilliant idea, where one only needs to change small aspects and get on with it.