As the PS Vita is a handheld console, it is designed for maximum power efficiency and battery life. For this reason you are limited to the options in the settings.
Is it planned to expose the option to the API to temporary prevent auto standby and keep brightness within the application? Even though PSM won't have all the functionality native development this requirement is really basic and exist in any high level APIs for handheld systems such as Android/iOS.
Seriously, this is a massive limitation and it is very important to expose this option...otherwise the PS Vita will be useless for any apps or games that don't requrie direct user input such as the accelerometer, videos...etc
We are the developers right? Don't limit our abilities please.
I'll raise this issue in Suggestions section.