I don't understand what you're saying here. You can easily do 4:3 pillarboxing on a standard 16:9 HDMI-centric display. In fact, that's what most modern classic console recreations with HDMI output do.
Personally, I'm all in on HDMI, so I prefer that rather than having to convert anything. Native is best.
I'm pretty sure you know a lot more about HDMI than I (and gaming in general, seeing that collection you have!)
But what I was thinking of may or not me relevant, but I was assuming that it is.
I have always preferred Sony TVs, and in the CRT days, they may have been superior. In the LCD days, probably not, but I still sort of like 'em.
On my Sony (a few years old) LCD, when I connect with HDMI, I don't get an option for 4:3. As a matter of fact, I never do. All you get is (upon hitting the "WIDE" button which should read "ASPECT RATIO" (but doesn't,), is "WIDE ZOOM", "NORMAL", "FULL", and "ZOOM."
Using those options and a Sony Blu-ray player I bought at the same time (several years ago) and hooked up through HDMI, the f-ing thing always stretches the picture. No choice. I WANT the "pillarbox" when watching old 4:3 DVDs. I was frustrated, then (long time ago) I decided to hook an old composite cable from the player to the TV....BOOM! "NORMAL" aspect ratio then correctly pillarboxed the old 4:3 DVD, correctly. Great! Except for the fact that I don't want it hooked up that way. I want the highest common denominator, and then I get shit-stretched video when viewing old "fullscreen" (4:3) DVDs. It really pisses me off, to this day. Evidently, the TV "assumes" that if I'm using HDMI, I want widescreen. It's not that big of a deal, because I actually prefer a small CRT for C64/A800 etc, anyway.
Would a 4:3 Commodore display stretch, or allow for pillarbox 4:3? Who knows? But S-video hooked to a 13" JVC TM-A13SU....
JVC TM-A13SU.jpg 68.79KB 0 downloads
....will leave no question, and give an awesome display that looks correct (even better for the time since this is a relatively high-performance monitor relative to the age of the C64) for the time period, and it is that which I prefer.
I am not "against" HDMI; it is rather natural for systems that support 720p or greater. Those systems suffer on an old CRT. The C64 and Atari 800 (etc...etc..) shine on this CRT.
That is what I was attempting to convey.