Yea, sure. But that doesn't mean he can replace an all time great pace bowler.
i am writing this not exactly as a counter argument coz we are not having a specific debate going here. it is given more as an example of my belief.
in a post WW2 aussie XI, for example, if miller is included as an all rounder and four bowlers are going to be chosen i would expect the four to be
lillee, lindwall, mcgrath and warne. if miller is sacrificed for an additional batsman the above mentioned four would still be the first choice. davidson, thommo, mcdermott, gillespie and lee - and miller too in the second option - would not be able to replace warne in either case.
in an all time aussie xi if spofforth and any other great is available for selection, one of the pacers would be replaced and it would probably be lindwall. and it will never be warne. in fact, any combination of a four member bowling attack you can think of for australia would feature a spinner for sure. and it will mostly be warne and on other times grimmett/oreilly. am sure benaud, border, waugh, taylor and bob simmo would agree with me. i've seen the all-time xis of some them.
in that sense one spinner in a four member bowling attack is a certainty for most countries - india, sri lanka, pakistan, south africa and england will definitely have one of bedi/chandra/gupte/ kumble/ murali/qadir/ iqbal/ tayfield/ faulkner/laker/ briggs/ underwood. west indies can do without gibbs but would expect sobers to bowl spin with their four man pace attack. new zealand would be struggling to field three bowlers - spin or pace - who could be a certainty like sir richard. they dont have the talent pool, unfortunately. still they may end up having vettori over most of their pacers as the fourth bowling option.
i guess i am trying to say one spinner is a must for winning test matches on a consistent basis. if three fast bowlers are not doing their job, the fourth is not going to do it either. you're better off having a spinner at your disposal.
btw, in a combined WI and Aus XI, warne is as much a certainty as Bradman and Sobers. (trumper, greenidge, bradman (c), richards, lara, sobers, gilchrist, marshall, warne, lillee, mcgrath). you will be able to change the other eight names but these three are shoo-ins.