Back to the AR-15 Barbie doll comparison you can convert an AR-15 to a piston driven style system with conversion kits that go for $300-400 roughly. Honestly if you're not good enough about cleaning your rifles that you like the idea of having to put less elbow grease in, the problem is the shooter, not the rifle.
CSM is absolutely correct on preferences between operating systems. I actively shoot all kinds of rifles and I honestly think that preferring one over another in a "all my rifles must be X" sense is bollocks. I like AKs and appreciate their design. I have practiced the profession of warfare with the M-16 and it's system and find it excellent, it's siblings in the AR family like I own now are similarly solid. I've fired some really weird operating systems and found they worked just fine too. If you're a responsible shooter who takes good care of their equipment your firearm will not fail you whether you're on the range, hunting or fighting for your life.
Meanwhile someone is selling this beautiful creation in my local.
Goddess DAMN I wish I had the 6.5k being asked for that beautiful classic. (Hollis 12 bore double rifle, it's got a closer relationship with field artillery then lesser rifles)
On a side note for the curious, the following's my current "shopping list" for various acquisitions in no particular order. This is the curse of the collector folks, I actively shoot, I hunt, occasionally I compete, and I carry for self defense but mostly I buy guns because I like'em.
Rifles:
.300 BL Upper
Mosin Nagant rifle
PSL rifle (aka the Dragunov knock off)
Ruger 10/22 (small semi automatic .22 caliber rifle, popular in the U.S.)
17XX Long Land pattern Brown Bess musket (Reproduction, I will never make the kind of money originals go for and if I did I would immediately donate such arms to a museum)
Sig 516 (modern variant that eats STANAGs*)
Mare's Leg in .45 LC (a pistolized lever action rifle, Zoey's gun in fire fly is an example of a mare's leg)**
FAL
Pistols:
Walther PPK (Yes. I'm a dork, got it)
Smith and Wesson Highway Patrolman revolver (classic American six gun)
Ruger Vaquero (reproduction of the Colt Single Action Army, /the/ six gun. in .45 Long Colt) **
Shotguns:
Double barrel 12 gauge**
Model 1897 Trench gun**
Expensive One Day Purchases: (every rifle on this list all told will run me /at least/ $2000, more when/if optics get involved)
IMI Tavor (the newly import legal civilian model of Israel's next gen assault rifle, and my one true love***)
M1A rifle (Not an M1 Garand, but in fact the civilian variant of the American M14 rifle)
Barret .50 Cal rifle. (Why do I want to be able to lob shots down range up to two miles? Because I can.)
*STANAG: STANdardization AGreement. Refers to a NATO document that standardized rifle magazines amongst NATO members. Such magazines are often just called "STANAGs". AR-15s/M-16s are the most prevalent rifle that uses STANAG magazines.
**These older arms are for competition in an American shooting league called "Cowboy Action Shooting" which is stupid amounts of fun. It combines cosplay, classic firearms and practical shooting skills in a glorious living history/renn faire atmosphere. It's directly comparable to modern three gun competitions which also focus on the interplay of "the big three" (shotgun, pistol and rifle) but of course uses modern arms. CAS is a bit easier to get into in many cases as three gun like most high end competition sports requires a lot of time, effort and money to even vaguely get good, CAS communities are a bit more greenhorn friendly and have more of a "fun" focus at the average event.
***The TAR-21 (aka Tavor)