Sorry, I hadn't seen this.
Antonio considered the breed finished in 1947 (though it probably wasn't), when he presented Añá. However, since he was shot in 1955, we will never know for sure. We do know he had stopped doing any public outcrosses. Agustín never mentioned any intention to introduce any further blood, though he might have done so when he came back from Canada and found the breed decimated.
The breed is still being refined of some of it's birth problems, like deafness, undershooting, etc. Concientious breeders focus on that, more than on adding any new breed. Doing the latter will mean starting all over again. You cannot realistically expect to introduce a new breed in the mix and see consistent results in, say, less than 20 years of serious breeding and culling. All dog breeds can offer unwanted ingredients that might only appear several generations after the first specimen is introduced.
I personally don't see anything in the Dogo that would merit introducing a new breed to correct. It is far easier to work from within the breed; we have over 50 years of experience to do that, which allows us to more or less know what we are doing. That being said, if you have lots of time, years ahead of you, lots of space and money (but really lots), and a large burial ground, you can do as you wish, meaning, there is no law against cross-breeding that I know of.