Why couldn't the CRJ100/200 be equipped with triple-string autoland? The gold standard for zero-visibility ILS approaches and landings is a triple-string autoland system, where the signals from the localiser and glideslope beams and the aircraft's radioaltimeter system1 are fed into the aircraft's autopilots and control its flightpath directly (with the pilots monitoring the system so that they can execute a go-around if the ILS signal is lost or an autopilot fails), cutting out the human middleman.  For redundancy, each of the aircraftside links in the chain (ILS receivers, autopilots, radioaltimeters, etc.) is present in triplicate, producing three parallel autoland strings, each constantly comparing its inputs and outputs to those of the other two strings, so that a failure in any of the components of the autoland system can be automatically detected and alerted to the pilots.
However, apparently, not all aircraft are capable of being equipped with a triple-string autoland, with the CRJ100/200 series being one of the major exceptions:

Simultaneously, pilot organizations globally were advocating the use of Head Up Display systems primarily from a safety viewpoint. Many operators in non-sophisticated environments without many ILS equipped runways were also looking for improvements. The net effect was pressure within the industry to find alternative ways to achieve low visibility operations, such as a &quot;hybrid&quot; system which used a relatively low reliability autoland system monitored by the pilots via a HUD. Alaska Airlines was a leader in this approach and undertook a lot of development work with Flight Dynamics and Boeing in this respect.
However, a major problem with this approach was that European authorities were very reluctant to certificate such schemes as they undermined the well proven concepts of &quot;pure&quot; autoland systems. This impasse was broken when British Airways became involved as a potential customer for Bombardier's Regional Jet, which could not accommodate a full Cat 3 autoland system, but would be required to operate in those conditions. By working with Alaska Airlines and Boeing, British Airways technical pilots were able to demonstrate that a hybrid concept was feasible, and although British Airways never eventually bought the regional jet, this was the breakthrough needed for international approval for such systems which meant that they could reach a global market.

Why couldn't the CRJ100/200 be equipped with a full triple-string ILS-III autoland system?  Even if it didn't normally come equipped with triplicate autopilots/ILS receivers/etc., those surely could have been retrofitted to the aircraft to give it full ILS-III autoland capability...

1: The localiser beam is used for lateral guidance throughout the entire approach until the aircraft taxis off the runway; vertical guidance is provided by the glideslope beam down to flare height, and the radioaltimeters thereafter.
I have experience on that program and can tell you that:
A:  While anything is possible, this would cost a fortune to implement, requiring a complete avionics overhaul.  For a single potential customer?  Snowball's chance in heck.  The customer would have had to commit to paying the development costs, many zillions, which would also have a snowball's chance in heck of happening.
B: By the mid 2000s, no development money was being allocated for that sort of product improvement on the 200. By then the program funding was generally only to deal with airworthiness issues and upgrades to deal with avionics obsolescence, as development money focused on the 700/900.
C: British Airways aside, there was no demand to speak of from the industry for that kind of capability, that anybody would be willing to pay for. Adding HUGs on the 700/900 to get Cat IIIa cert was more than sufficient.  On the 200, even to do that would have required an avionics suite upgrade that no regional operator would be willing to pay for (again, Snowball's chance in...).  Regional operators run on very thin margins.
In the US, by the late 2000s, Regionals would not even implement optional Service Bulletins unless there was a financial payback of ONE YEAR or less.  That meant that only SBs mandated by Airworthiness Directive were being incorporated.