Are there many people who have seriously done it, say to create a dog with four breeds? I can only assume its a big commitment and a high % of failure.
Say, Source a decent pure bred, cross it to another pure bred, keep the progeny, raise it, work it test it over several seasons and if it comes up to scratch then breed it to maybe a F1 which has also come up to scratch? I should think after all the planning, research, and finally breeding the dog only to realise it falls short of the bench mark, must be soul destroying however the chances of achieving to breed a dog of the type you set out