Who knows how good he would have been? Probably not as good as he was, of course. But from a young age he would have worked on being, say, a power baseliner. And thus developed his skill in that manner.
The real answer is..we do not know. Certainly there are players I know of who 'converted' from serve and volleyers to baseliners, with success. And, of course, vice-versa. But not everybody can. Could Pete Sampras have done so? Maybe, maybe not. Nobody knows, however.
5.0 game with 2.0 consistency.
Babolat Pure Control Team 98 (348g 330 SW 9.5pts HL)