There's a lot of things about the market that I can think of but a simple straight forward point is:
Markets always change. All traders deal with this.
The success rate for system traders and discretionary traders are the same.
It's a matter of time for these system traders to become a part of the noise.
We all work with the same data. What you see is seen by others.
Van Tharp has the right idea.
Remember that his books are an introductory / newbie books.
Good thing is you are having doubts and questions about "conventional" knowledge. Very healthy for a system developer.
Reality of intraday trading????
??? I don't get it. What's not real about it???
Is this like paper-trading or back-testing question???
...
Is this like a Descarte question???
You won't be successful (with whatever team you are planning on running) unless you know about system trading very well.
Too many ways to fake it.
In terms of back-tester and execution platform, it won't be hard to find.
Basically, you have a longer timeframe trading and a shorter timeframe trading fused together.
If you can make money just by trading your scaling in/out timing, via out-right that's value added.