The first is the "number of requirements" problem. At most colleges, there is some limit as to how many courses can be required for the major—a practical limit if not an explicit formally-imposed one. A lot has been forced downward into the standard two-course intro sequence, and this has "worked" because some of the students are either brilliant or have had good preparation in high school, where that "two-semester sequence" can be spread out over multiple years, and in many cases is preceded by one or more years of "pre-AP" computer science courses. But the downward migration of material has meant that what we now consider to be a standard computer science degree includes a lot of material, and if we add some sort of college equivalent to the pre-AP courses, we can either add them as explicit major requirements (that some students can place out of), which means removing material from the other end of the major, or leave them as bypassable prerequisites, implicit requirements that mostly serve to discourage students without a high school CS background from taking CS.
The second big problem is the staffing issue. As a practical matter, every course that might get added at the pre-CS1 level will be viewed as an "extra" that has to be staffed, and either takes away from staffing that could be provided to upper-level courses—earning the ire of at least some in the department—or else requires additional hires and thus administration approval. If it is played as "we need this as an additional prerequisite to CS1", it will find an administrative reaction of, "how did you get by for the last few decades, then?" If it is played as "we need this to get some students up to speed before taking CS1", it will find an administrative reaction of, "why are you proposing to teach remedial courses at the college level?" There is also likely to be an uphill battle to even fill the course, especially if you can't get the college to let it fulfill some general education requirement, and then you have the added problem of trying to justify offering a course that is chronically underenrolled.
Adding to the campus-politics tangle of the whole thing, CS is often viewed as too mathy and/or vocational training and therefore viewed with distrust by members of some other departments, making it even more difficult (in some cases) to argue for needed changes.
So, it's a hard problem. Good analysis, though.
 Which isn't actually anything like standard, actually, but we still talk about it as if it is. It's at least the case that formerly-advanced topics are now widely present in the first few courses.