The .17 HMR would require a completely different design, seeing as it's essentially a rifle cartridge with a rimfire primer. New magazines, new bolts, new barrels, and possibly not being able to use polymer upper receivers.
.17 won't require anything stronger than the current polymer receiver. Recall there are 5.56mm versions with polymer receivers, upper and lower. All the receivers do here is keep the parts out of the rain and in the right positions, neither is stressed in any way. In the 5.56mm versions the bolt locks into the barrel extension, not the receiver.
There have been attempts to make a semi auto .17, but the firearms have experienced problems because the .17 is so fast that the blow back system can't handle the round. Also see the previous post where Remington has recalled all the semi auto .17HMR's and gave the owns coupons to buy a .22LR.
Check out Alexander Arms, they make an AR15 upper in .17HMR. I was thinking about getting one but after reviewing the ballistics of the .17HMR, there was no advantage to the extra expense for the ammo, nor the cost of the upper, the 22LR gets the same results for me at a lot less cost. But again that is just my opinion.