I have used a thirty caliber for fifty years. My first was a 30-06 and I chose it because I could load light bullets and match the ballistics of smaller calibers for varmints, a medium weight bullet for deer, antelope, and such, and heavy bullets for elk, moose, and the like. The idea worked for me and I had success with that. After a while, I just used a medium weight bullet for everything but the larger animals. I still used heavy bullet loads for them.
I later added a custom 300 WM with a muzzle break for long range work. The 30 caliber has so many bullet choices and loading data that I was able to get along with the 06 for one all around rifle and have less dies and components to stock for reloading good useful cartridges.
I also used a twelve gage for all my shotgun needs. For most of that time I used a 44 for a handgun round. I have since added a 45 acp because of the civil unrest. Also I fell in love with the 444 marlin rifle and justified it because like the thirty caliber rifles, It used the same bullet (although a variation) as the marlin 44 magnum and my 44 handguns. My molds are used for the same guns, only the sizing dies are different diameters.
I also swage thirty caliber and 44 caliber bullets to fit my needs for jacketed bullets.
To be completely honest, I probably still have as much reloading stuff as other people, but because I stuck with one caliber, I believe I was able to have more top quality tools and stuff to address making top quality ammunition than had I chosen many different calibers. Primers were much more simple to stock also. It is not for everybody, but I get your intention and for me it worked out just as I had hoped.