7 HDMI Inputs required! and source switching off?

[aml_]

55Q80R

I have 7 devices fighting over the screen. My plan is this:

HDMI1: PVR, Blu-ray, Wii  <- these will share an HDMI via 3-1 multiplexer. They are all normally off, and are only used one at a time.

HDMI2: Raspberry Pi <- runs OSMC. I'd prefer this to be powered by the high current TV USB port. This though maybe does not appear to be a good solution when combined with CEC.

HDMI3: Chromecast <- because I'm now finding out Samsung compatibilty with phone's casting apps is really really bad (Youtube is OK, BBC, ITV, all4, NowTV all not seeing TV). Same as the Pi, would prefer to be powered by TV.

HDMI4:  Soundbar (arc) - it is a neater solution than optical for control.. and seems to work.

<edit: this equals 6, well done eagle eyed viewers! >

Issues: CEC:   so it's either all or nothing in terms of control and auto detection/source change.  Problem with sourcing power for my Pi is that after a few seconds after power on the TV will switch source to it, when I don't want that.

If I want to use CEC, I need to power the Pi and chromecast from a fixed supply (i.e. leave always on), or I don't use CEC, in which case the soundbar will be optical as using HDMI is a waste of a port.

CEC is not a dealbreaker in most respects. But most useful for the soundbar (Polk magnifi mini) because the IR receiver is very directional and my Harmony remote doesn't work overly well with it.

Are CEC and ARC independent of each other?