Actually, it’s a very interesting idea. It may be possible to make it all the way to orbit and back with a balloon and some low thrust ion engines.
There’s a company that’s put together a plan for an orbital balloon concept that works like this:
First, a large lighter-than-air floating station called “Dark Sky Station” is built. This is an interface between earth-bound balloons and a much larger orbital balloon.
From the ground, a large balloon called “The Ascender” transports materials and personnel to dark sky station.
At Dark Sky Station, a much larger balloon, equipped with ion engines, departs for orbit. This balloon isn’t shaped like a standard spheroid balloon, but instead looks like a large ‘V’, and is designed to move horizontally at high speed in the thin upper atmosphere and to use aerodynamic lift as well as lift from lighter-than-air gas.
At first, it uses standard atmospheric lift from being lighter than air. But then it starts to accelerate forward very slowly, and supplements its lift by hitting molecules and pushing them down. Eventually, the atmosphere becomes thin enough that it can’t support the ship, but by then it’s going at orbital speeds and can reach obit on ion propulsion alone.
On the way back, it starts its ion engines to slowly (very slowly) de-orbit. As it hits the first molecules of the atmosphere, it slowly descends and reverses the process, and eventually floats back to Dark Sky Station.
You don’t need heat shielding, because the deceleration through the atmosphere happens so slowly that the ship never heats up.
Is this feasible? As a rough proof of concept, maybe. It seems plausible, anyway. The real question is whether it can be made to work as a practical means of getting into space. If it can, it’s a huge breakthrough that could lower the cost of getting mass to orbit by orders of magnitude.