Is it actually possible to intercept the glideslope from a completely power idle descent (ATC permitting)?
Yes, it sure is.
However the Airbus (A320) autopilot/Flight director wont capture/engage the Glideslope until the localiser has been captured/engaged first.
You do not have to be in level flight to achieve this.
You can be on (idle) descent or even rolling out of a (descending) turn !!
Sometimes ATC
you around and so you got no choice to intercept it from an idle descent (sometimes from above the GS too)