Could super-heated gas allow for Dirigibles/Zeppelins/Balloons to go higher than 60 km of altitude? Well, I don't know much about physics in general, so I hope I don't make too many misconceptions.
So, from what I could read in this Wikipedia article, the balloon named "BU60-1" achieved the altitude of 53 km. It is not said what kind of gas was used, but in the website sourced in Wikipedia article (here), it says it used pressurised air. The whole intention of the record-breaking attempt was to make a thin airbag light and resistant enough to break the record, which they did.
But, let's just say that for some reason, we want to make something really heavy and big fly, such as a rocket.

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*The question:
So, the thing is that even though you could simply make a bigger Dirigible/Zeppelin/Balloon to lift something heavy, the limit would still be something around 40 km of altitude (I think).
So, even if I heated air (or plasma) to enough temperatures that the Dirigible/Zeppelin/Balloon would achieve or surpass the buoyancy of an aircraft of the same size using Helium or Hydrogen, it would be possible to surpass the 60-200 km altitude?
Or even so, it wouldn't be possible to achieve such heights simply because you wouldn't have too much increase of buoyancy compared to other gases?

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*The "why":
Simply put, I'm just wondering if there could be a way of making floating platforms to lift rockets, so they don't need their first stage. Or, at least, to make Zeppelins (a dirigible with rigid structure) to be smaller than conventional helium/hydrogen Zeppelins (but even so, I doubt it).
Of course, I can imagine that if such thing was even efficient, nations would already be using that.
 A: You will not get a huge advantage by heating the gas, after all you would need to carry the considerable weight of the heater. Even at very high altitudes, provided the gas inside the balloon is not at a higher pressure than the surrounding air, due to the tension in the balloon envelope, the ratio of the weight of the displaced air causing the buoyancy, to that of the gas inside the balloon will be the same as at ground level.
The net buoyancy is the weight of the displaced air minus that of the internal gas, envelope and payload combined. So the real limit on the ability to gain altitude is the weight of the envelope and payload. When the gasses both inside and outside the balloon are rarefied, you need an envelope of enormous surface area, so it needs to be incredibly thin and light. Perhaps you need graphene for the next world record.
A: The main thing you need to achieve orbit is very high speed, not merely high altitude.  Look online for Newton's Cannonball.  Rockets are about the fastest things we know how to build, and they also carry their own fuel and oxidizer so can work in a vacuum.
Compared with the effort to achieve such high speeds, the effort to reach high altitudes from the ground is a relatively trivial addition.
With that said, companies like Virgin are starting to launch small payloads from planes, so there is a small gain in starting higher.
