I would agree "Being obsolete" should lead to a reduction in demand, but not zero demand. I know people who use none smart phones even now.. Retro gaming/CRT TV's would be a prime example, while they are technically obsolete, there is a healthy market, so if you had a warehouse full of CRT...

I will buy their stock so I have 51% control, and then 3 days later they issue new stock and now I have 40% control. Its very frustrating, how do I stop this?

These futuristic designs are out of place if you consider the overall style of the graphics. If they must be included, then please consider adding the option to use classic Capitalism 2/Lab graphics.

Or they can add an auto buy of public shares function. When a company issues new shares or someone sells their shares, you buy it automatically. Thus you don't need to monitor financial news all the time.

my main preference with this is, that the player should not lose the game if they lose control of there parent company, if they have funds, they should be able to found a new company - as the AI's do

This will be changed as you suggested in the next major version 10.1.