Who are you agreeing with? I said that if centre content is going to be extracted, then it makes sense to allow user control of the extraction level. The extraction process is ocurring anyway.

That's very different from remixing three discrete front channels by bleeding centre content into the left & right speakers. Who says a user adjustable remix capability is trivial? Besides, support for 2.1 and 4.1 speaker configurations already exists (and the solution is not a variable bleeding of the centre channel content, as you're proposing). Buy a mixer. After everything companies like Dolby and DTS have done to introduce a discrete centre channel to consumers, they're not about to create technology that lets you spread discrete centre content across the front soundstage. That goes against all they've worked for since the Pro Logic era. I would, especially based on your description: "the signal drops off rapidly to the sides (so instead of misplaced center, you get almost no center)".

The very point of using a centre speaker in home theatre is for the benefit of off-axis listeners. If you are using a centre speaker whose output basically disappears for off-axis listeners, then you most definitely have a speaker dispersion problem. Remixing the front three channels is not a solution to a center speaker with problematic dispersion. By bleeding the centre content to the other two speakers, you will be reproducing the dialogue in triple-mono.

This will not only introduce comb filtering and problems with dialogue inteligibility, but will cause the location of the dialogue to drift away from the display and towards the speaker that is nearest to you. After all, you no longer have the dialogue locked in the centre speaker only.

Again, this goes against everything that Dolby, DTS, THX and others have tried to do for dialogue reproduction at home. So don't expect any of them to come out with processing that allows you to remix the front three channels. A quick clarification on nomenclature: PLII creates up to 5 output chanels; PLIIx creates 6 or 7 output channels. The sub output is not created by the processing but by the bass management system in the receiver. There are several reasons for steering 2 surround channels over 4 surround speakers:

Localization: A car leaves the left side of the screen, the sound disappears to your left. A plane flier overhead, the sound disappears behind you. Even the two best surround speakers in the world can't be in two locations at once (at your sides and behind you).

Stability: No matter where you're sitting in the listening area, sounds that are intended to be heard from behind you are always heard from that direction. No magic involved, just a pair of speakers physically placed behind you (makes it hard for those sounds to come from any other direction).

Envelopment: Four surround speaker can literally 'surround' you better than two speakers can. What "mangling" are you talking about? If you were sitting in the sweet spot, right in between the two surround speakers, any correlated mono surround information would end up phantom imaging behind you. If you're out of the sweet spot, those sounds collapse to the nearest speaker.

PLIIx extracts those sounds and sends them to speakers behind you. Now even if you're out of the sweet spot, those same sounds will always image behind you.

Same exact directionality, just greater imaging stability. You really consider this "mangling"? That makes no sense. Dolby and DTS and THX were already recommending the use of two rear speakers for EX/ES playback. Dolby extended PLII to PLIIx because they noticed that 7.1 set-up were catching on with consumers. The fact that people were using two rear speakers was the justification for PLIIx, not the other way around.

Finally, despite your explanation, I still don't understand why you would deliberately refer to digital surround processing as "analogue". Again, it's probably just me.