You can submit emails to Canon technical support with your requests and they will be read. You will get a polite email saying your requests will be considered and/or forwarded to the appropriate people. Here's to hoping they actually follow through with that...
5D Mark III email support:http://usa.canon.com/cusa/support/consumer/eos_slr_camera_systems/eos_digital_slr_cameras/eos_5d_mark_iii/form_display/support_by_kb_email
I've asked for:
1) Illuminated focus points
2) f/8 AF (they have promised this now)
3) Old zoom functionality in addition to new (I still hate the slow wheel zoom, but love the instant zoom)
4) Allow "Flash sync speed in AV mode" in "My Menu"...5D2 and 7D have this
5) More minimum shutter speed options
6) EV with auto-ISO
7) Built-in intervalometer functionality
Clean HDMI out (they have promised this now)
9) 1080p 60fps
10) Better dynamic range in future sensors
Regarding AF point and exposure linking, I too really wish the feature was available on the 5D3. I posted about this a few weeks ago, so I'll copy it again here.
On the 5D3, the density of the focus points versus the density of the metering grid does not match well, so I don't think that this is a likely 5D3 feature. The 5D3 and 7D share the same 63-zone, 9x7 grid. On the 7D (which has AF point-linked exposure), the focus points directly matched up with the exposure metering region, as can be seen in this graphic from the-digital-picture.com 7D review:
So AF-linked exposure was a no-brainer on the 7D. Not so on the 5D3. However, on the 1DX, the metering grid is now 4x more dense (252 zones or 18x14), plus it has the 100K pixel RGB metering sensor, so it can match up the regions and pixels closest to the AF point with much more precision.