Once again, that's your reality. But head-case long hitter remains a small subset of golfers, and even in that subset there will be those who benefit more from another wedge or hybrid than a second putter. You leave out the potential problems that use of two putters add to the mental mix, seeing only the benefits they've given you.
Actually, I think almost all of golf is one giant set of small subsets, and I'd guess there are a decent number of players who would benefit from Shivas's approach. All the many combinations that even excellent players, such as Jamie, MWP, David Ober, etc., utilize when it comes to woods, hybrids, and long irons certainly implies to me that they are specialty clubs and don't come into play nearly as often as the putting aspect of the game, so I can easily see Shivas's approach, and wouldn't even question it.
Heck, if there were a putter that helped more with lag putting from 40+ feet, I might add that. I wouldn't even need to drop one; I threw in a couple extra clubs yesterday just to get up to 14 in my bag, and still noticed that I had a practice club in there that I don't use in play currently. Short putts are no problem right now for me, but I am a lousy lagger. Of course, that is primarily a function of how infrequently I play and practice, not the club. (And in case you missed it, that means I actually played yesterday - well, 11 holes in intermittent rain and lightning, anyway!)