You're still missing my point!
When you compare the OM1 to the OM-D EM5 (sidenote: why not just call it the OM-D1?), the additional thickness caused by the mirrorbox is not all that great. The bizzare thing is that small differences in overall dimensions don't seem to be as important in determining bulkiness as other design factors. The OM1 and OM-D EM5 aren't that much smaller than the Rebel, but they both appear to be so (to me at least) because of their cleaner lines. With prime lenses and careful design DSLRs needn't be anything like as bulky a system as they currently are.
Ah, now I get your point! I thought it was exclusively a matter of absolute bulkiness, but now it's clear to me it's more a matter of style and design. And yes, I would love such a camera from Canon, a retro styled APS-C or FF digital reflex. Actually I'm in for the Fuji X-100s, but a retro digital interchangeable lens Canon camera would be cool, many recent small EF lenses from Canon would fit it nicely. But you must admit your point was not that much evident in your original post. Maybe in a near future, when thinner OLED and compact sensor assemblies will be available, the thickness beyond the focal plane, previously being represented by the film and back only, won't grow too much, and such a camera may pop out, I'm sure it would be appreciated not only by you and I.
Perhaps Canon could make a smaller DSLR as a modular system (like the OM1 popularised back in the '70s), or even a modular EOS-M series with hand/battery grip options and something like the Sony LAEA2 adaptor (with moving mirror and a pentaprism -go on Canon, take up the challenge!). This latter option would be a good way of enticing EOS system users to buy into the EOS-M system as well: use EF-M lenses without the adaptor when you need maximum compactness, or swap in the adaptor, battery grip and EF(-S) mount lenses when you need performance (the elephant in the room is full-frame and whether Sony will make a full frame NEX stills camera...)
This, and our previous mention of batteries, made me meditate on a curious thing about grips, in that they first appeared as ugly, undesired but necessary bulges to house bigger batteries for the rapidly growing electronics and automation in cameras; I remember a well known italian photo magazine, in the pre-internet age, complaining for how uncomfortable the unusual feel of that "angulous" protrusion was. What can't be cured must be endured, thus hand grips evolved, and also the way we handhold cameras eventually, so today you have to purchase them as expensive accessories for those cameras which don't have an ergonomic grip (think of Leica) if you want to feel comfortable, because we're used to this feel which, indeed, is better. This is making a virtue of necessity, but don't you think it's a bit funny?
The comparison between the Rebel and the OM-D was made because I could find side by side comparison photos of them and I could also find side by side shots comparing the OM1 to the OM-D, but I couldn't find any shots comparing the Rebel to the OM1. If you can find the latter, or are willing to photograph them yourself (assuming you own a Rebel), I would be most grateful if you could share the photo.
Traveller, sure I can find an OM (except for the 4) because I've got the 1, 2 & 3, the problem is the Rebel, since the one I've got is the original one, the 300D (and this explains why I am interested so much in the forthcoming APS-Cs
), which is way larger and heavier than all the others from the 350D on, it wouldn't be a worthy comparison. Anyway, the link you provided shows them both, evenly scaled though not side by side, so a bit of cut & paste would do the job. Nevertheless, if you're interested in the unfair comparison anyhow, I'll be glad to snap the elephant and the gazelle side by side, it seems we share a common passion for this kind of stuff after all!