My complaint about the KG era was that aside from '08 & '09, many of our regular season outings were not so spectacular, given the talent on the roster. Sure, the whole notion of 'Sheed taking a vacation during '10 was evident, however, in addition to that, teams would play us, 5 on 4. It was clear that as time went by, more and more opponents were challenging Rondo to take the open shot.
I suspect that if there were a 23 year old Walker on the KG squad, an opponent would always play 5 on 5, daily, because if someone sagged off Antoine, he would set his feet correctly and take a 50 FG% jumpshot, since he could in fact, shoot the ball (given enough time to get setup), despite his general poor shot selection in other areas of the game.
And unlike Rondo, he wouldn't grow bored during the regular season and run around dribbling the clock down, half the time, waiting to rack up another assist. Instead, 'Toine be like KG's second voice of enthusiasm but with a bit more humor than just pure intense fire and rage. The C's would have regular ball movement and then, we wouldn't have had so many pointless losses, saving ourselves for only the playoffs. I believe that we would have been a 55-58 win squad in 2010 and may have even had home court, over the Lakers.
And then, as for Playoff Rondo, the C's would not have dependent upon his Dream Shake floating antics, to have advanced. There were enough ways for the C's to put points on the boards.
Since Walker was a point forward, his job would not be to guard quicker guards. I'd say that Tony Allen, Ray Allen, and PP were equipped for that role. Walker's job would be to create ball movement, find mismatches to help in scoring, while assisting on taking the defense pressures off the Big 3, as he'd also be a scoring threat at any time.