why a custom built converter isn't for everyone....

Call a custom cam grinder... "need to know what converter you are using" . So call the custom converter shop "need to know your cam specifics..."
At that point again the intended purpose would need to be discussed for both of them...
Where you could do is have a different vehicle for a different purpose. Like have two Vans three cars and two trucks or maybe even more LOL and build each one for its own purpose...