The only reason I would consider a rimfire AR would be to use cheap ammo in it, and neither the .22 WMR or .17 HMR is cheap compared to .22 LR. Lucky Gunner is showing .22 LR as cheap as 2.8 cents per round and the cheapest .17 HMR they list is 22.5 cents per round, over 8 times as much. And there's .223 Remington at 20.5 cents per round, so it's cheaper to shoot .223 in an AR than it is .17 HMR.
Winchester Super X .22 WMR 40 grain JHP ammo isn't as bad at 17 cents per round. I don't know how the price of an AR built for it compares to the Savage rifle but the A22 Magnum is what everything I look at would be compared to.