Sion
Propellerpilot is right - he describes the way most pilots/companies/authorities handle the sion issue.
The steep approach plates for your aircraft show the case of a final approach leading directly to touchdown (e.g. London City), where the aircraft needs to fly a stable approach and be able to do a safe g/a at the minium (taking into account the higher energy due to steep descent)
At LSGS the final approach is a visual 3,5° segment, as long as your aircraft is able to do a normal 3,5° ILS you´re fine .
For the IGS part, - fly in landing configuration or intermediate flapsetting - to fly at a stable speed and ROD - even with A/I on. I have not yet found a restriction on the descent angle for intermediate approaches or enroute descent in an AFM (but off course there might be one...)
my 2 cents
welle