This is not necessarily an opinion of mine, but an observation, of sorts.
You see, Paul was not perfect in his abilities. He was an incomplete version of what the B.G. hoped for which only added to their concerns. What is meant by this is that he was "trapped by his own prescience", also by his inability to bear the burdens on his mind, he was forced to make concessions. The longer that he waited to "disengage" the more finite his options became. Some examples of what I mean is when his first son, Leto II was murdered. At this point Muad'Dib followed his own path of revenge which only led to further divergence from the Golden Path. However, he still had the option at that point to do what Leto III (aka God Emperor) knew had to be done.
Upon a sand dune toward the end of Children of Dune, Leto and Muad'Dib have their brief discussion about their roles. Leto informs his father that he intends to take the Golden Path and is chided by his father for this. Knowing the suffering and sacrifices that his son would have to endure, this was his natural reaction.
However, Muad'Dib is then chided for not choosing the path. Accused of ignoring his purpose, the TRUE "terrible purpose" which is often mentioned.
Muad'Dib's shortcomings resulted from his indulgence in selfish love as opposed to the self-less, unconditional love that is the fuel for the Golden Path. By taking a bride of sorts and having his children, he was attempting to cheat his fate. Knowing deep within himself that he was never intended to enjoy those things, he indulged in them anyway, only to have them taken away.
We can clearly see in Leto that he had no love except for the love that he shared with Ghanima. It is noted in the books that Leto's transformation was allowed to finally reach its completion upon the death of his sister. For Leto II no longer had any emotional attachments to distract him from the path.
We see also that when Leto II(III) finally opens his heart toward Hwi, he starts to become progressively careless. Then again, he was a hopeless romantic...
So yes, I think that the B.G. intended to achieve a prescient Bashar, but instead ended up with Paul whom was capable of much, but also incapable at the same time because of the 'gap' in his genetics. This is supported by the fact that Bashar Miles Teg gains his own KWisatz Haderach type powers prior to the end of Heretics of Dune. The B.G. were always wanting to flirt with the possibility of having a K.H. but not enjoying the true cost of having one in existence. (Remember that Miles was Atreides just the same as Ordade, Paul, and Leto I,II, & III!)
To end this comparison, I would like to also say that Leto III saw that necessity of ignoring his own possibility of demise to ensure that his actions remained selfless, whereas the actions of Paul were dictated by possible futures of his own death or those around him.