Yep, reverting to stock is simple with our remote tuner, you can do it from home
The important point here is the definition of 'custom'. When a project for a vehicle is created it is then the 'optimal' map for that vehicle with that setup. There is no need to create a 'custom' tune - every engine is very similar in output (nowadays) and even then the ECU adapts to smaller changes. The whole generic/custom debate is really only for older/simple ECU's.
The only time you would need to create a custom tune is for a setup you've never come across. Most reputable tuners also retain all factory safeguards.