I have been looking at Wilton for my Belisar mare simply because Now or Never M is not available frozen and the Belisar x Now or Never match is a very good one, so Wilton might be a good alternative.
Any of the stallions with Now or Never on top and Saros xx/Belisar through the damline will produce well-rounded horses that can perform both sports fairly equally well, especially since it is Belisar who brings in superior temperament, rideability, elasticity and gaits.
You asked specifically about Wilton or Uccello, both share a similar damline - both top and bottom lineages are stallion producers as well producing exceptional broodmares.
2012 Das Goldene Buch: Der Springvererber mit Top-Zuchtwert Now Or Never - revealing he has produced Alchimist, Toronto, Uccello, Uno, Valentino, Vallado, Volkonsky, Wilson, and Wilton, to name a few. Basically, he has stallion sons standing in Germany, Sweden, Holland, United States, Russia, Spain, and Belgium.
The Belisar damline is found specifically in Valentino, Wilton, and Toronto - the Keur TB stallion Saros xx sired Belisar. As an aside, Belisar has also produced the dressage stallions, Kroonjuweel who has an index of 150 points and is rated a top sire of performance horses, and Houston who was SPT champion and has himself already produced 3 stallions, all of whom were themselves SPT champions. And I believe he has a son in the UK, and also the USA, but I could be wrong about the last one. Belisar is long dead now, but still carries a reliability index of 93% in Holland and his list of Ster, preferent and prestatie mares is impressive.
So, either lineage is a very strong one to capitalize on. I am not sure I agree that Belisar would squish the jump per se, because it depends on what mare he was paired with. He performed equally well in both disciplines and sired for both disciplines. My own mare is a testament to that who was shown jumping and always in the money. She has a strong competitive spirit. Her daughter has never placed lower than 2nd and again shows similar competitive spirit.
If you want to avoid Belisar specifically, 3 stallions pairing Now or Never and Saros xx are Vallado (now called Praise) who used to stand at Silver Creek, and Alchimist and Uccello both standing in Germany.