[lukebuehler]

I did not say that the overall model must be built on intraday data.

But most models will simply be useless without proper execution. And IMO, the model should be back-tested with simulating the transaction costs as close as possible.

So the overall model might be fine and interesting, but if you can't close the loop with a proper execution model, which usually affects the overall model as well, you simply don't have much.