I'm not sure anyone will disagree with you so
why presume that anyone will try to serve you any kool-aid? If they do, you can always respond but to issue an unnecessary challenge up front just invites a minor flame fight that will accomplish nothing. Most of us are here to discuss and learn, not argue -- there are plenty of places that thrive on that.
Couple of historical points
"Back in the day" when the US did use a regimental system (I'm using the post-CW period for the example) there was no such thing as "up or out." Career privates were common, and it wasn't unusual to find a company first sergeant with 15-20 years in, most of that as an NCO. Officer promotion was slow, mainly because it was done based on regimental seniority until the rank of colonel and branch seniority thereafter. Root's reforms (and some work done prior to him) changed the officer promotion system, but the enlisted side remained more or less "as was" until later.
US regiments did not have home areas. Such a concept was discussed in the Cavalry Journal (and other sources) many times (I'm familiar with a couple in the 1880s, but those weren't the only occasions), but was usually struck down as "Prussianism" (a code word for fearing a garrison state) and never went anywhere. Rotations tended to happen every few years (more for a crack regiment...less for one that was not in high demand), and involved moving the entire regiment (or consolidating it, as was the case with the 7th Cavalry prior to the Little Big Horn...two and three company posts were the order of the day back then). Later, moves were still conducted on a regimental basis. You saw this even with Philippine garrison duty; cavalry units would simply leave their horses in place and exchange stations with a regiment already "in country."
Even under this system, a man could transfer to another company within his regiment, or change regiments by enlisting in a different one when his current enlistment expired. Some transfers did take place between regiments, but they weren't overly common. Officers would often refuse promotions if a vacancy came open in a different regiment, although over time this became less common (15 years as a lieutenant was enough to make many want to test new waters).
Downsides could be stagnant development (although this varied greatly depending on the personality of the regimental commander) and the formation of cliques. Plus side could be tremendous loyalty (to first the company, then the regiment) and a continuity of knowledge and experience that might otherwise not have been available.
Indefinate Re-enlistments
The Army and all it's wisdom some years ago decided that E-6 and above with 10 or more years have to do an indefinate re-enlistment. My thought on this is to make it an option and in doing so the soldier re-enlists indefinately for that post. Many with 10 years or more in service have families, this would stabilize the family, additionally would set the service members up for retirement. Imagine knowing the last 10 or so years of your career would be in the same location. Move soldiers all over the first half of their career and then allow them to stabilize themselves and their family if they choose to do so. There will be those who want to continue to move and those who will want the stabilization. Just my .02 on the subject.