The biggest problem with this question is the scale of that diagram, to give you an idea:
- The earth is 63.7x the height of the atmosphere in radius.
- This means that leaving the earth horizontally will encounter much more atmosphere than shown.
A plotting of a circular model of the earth with atmosphere/without using equations shows this:
Wolfaram Alpha Scaled Plot Here
But, more importantly, we want the intercept of where you'll be horizontally leaving the atmosphere...
So, basically, you're going to choose to travel through 1133.22km of atmosphere instead of 100km. You're doing 11.3322x the work to do what you've said (simply put, not including massive complications from prolonging a bunch of other stress on the materials). The goal is to minimize stress on the materials, if you've chosen to prolong stress to any substance you're jeopardizing the mission.
Once again, I am an amateur, let me know if any of this is wrong. Note, this information is simplified:
- Does not include earth rotation.
- This assumes the earth is a sphere, not true.
- As JCRM pointed out the atmosphere is a gradient, so the amount of total atmosphere passed through is significantly less than 11.3322x.
- You are increasing time at max Q though, because the gradient is more spread out.