Lusthansa,
One step down planning for alternates as you put it, is used at dispatch and it works like this. (JAR Ops 1)
Actual Available Approach - Required minima
Cat 3 - Cat 1
Cat 1 - Non-prec app(can use LOC minima) *
Non Precision - Non-precision + 200ft/1000m RVR *
Circling - Circling
(*cloud ceiling required as well as viz/rvr)
Cannot remember seeing island reserves but you are allowed to dispatch without alternate if multi runway and weather above a certain level. Minimum 15 mins extra fuel has to be loaded in lieu of alternate fuel.