I have one lower with a match grade trigger assembly and three uppers. This way it keep the costs down to a minimum. Besides, you can't shoot all three at the same time so its no big deal. I have a .22lr upper, a .223 M4 upper for tactical matches and a 20" A2 HBar for longer distance shooting. I wouldn't mind getting a 11.5" upper just because.
I like the one lower, multiple uppers idea myself. It lets you trick out just one lower instead of several lowers. Think about putting a match grade trigger into each lower you own. How about a collapsible stock on each lower. It can get very expensive.
I shoot competition that requires you to shoot x number of rounds rimfire and x number of rounds centre fire which means you have to shoot two rifle types during the relay. Most people I shoot with have say a 10/22 for the rimfire part and maybe something like a Tika Tactical for the centre fire part. I just switch out uppers and am always shooting the same rifle so to speak. It works great for me.
BTW, Accuracy Speaks, as mentioned above, is also very good at building uppers in .22lr but there might be a longer wait time as they are a small outfit.