Tom said above that the climb was less than 10 metres... which is manageable... But it may be some distance laterally as well...
Obviously you'd lose your returning nines... Tom also mentioned above that the balance of those nines would be thrown out...
Would the "feel" of the course be compromised by having six dramatic holes (current 10, 11, 12 plus three new ones) all in a row surrounded by the less visually dramatic holes on either side?.... I don't think it should... Despite a love of the first three holes, the routing of the current holes 1 to 7 do form a certain back and forth feel and this will be reduced by starting at 4 (which is one of my favourite holes)...
I think that in all but a very, very select few minds, the new three holes would add both to the quality and reputation of the course...
But I do like Rich's idea of 21 holes