Hello DrIsIN
In reality it would not be possible to have each done at he same time. However in practice double procedures like endoscopy ( as in gastroscopy) and colonoscopy can be done one after the other under conscious sedation.
Conscious sedation is a combination of medicines to help you relax (a sedative) and to block pain (an anesthetic) during a medical or dental procedure. Normally used meds in the UK for this isxylocaine and fentanyl or pethidine .
With regards to the bronchoscopy, a bronchoscopy and gastroscopy cannot be performed together as both are performed using the oral route. With the bronchoscopy they use a bronchoscope to examine your throat, larynx , trachea , and lower airways. It can be performed using a throat spray ( usually xylocaine) and Midazolam. With a gastroscopy , they use a gastroscope to examine the the oesophagus (gullet), stomach and first part of the small intestine (duodenum).
A cystoscopy is a medical procedure used to examine the inside of the bladder using an instrument called a cystoscope. A cystoscope is a thin, fibre optic tube that has a light and a camera at one end. It's inserted into the urethra (the tube that carries urine out of the body) and moved up into the bladder.
With a cystoscopy you are asked to lie on your back , while with a colonoscopy you will be positioned on your left side with knees, so it will not be possible to perform both at the same time plus you need to be very aseptic when performing a cystoscopy.
But as RNinCA said this should remain a "fantasy" as the dangers of playing with endoscopes and sedatives are life threatening.