I don’t think it’s a bad idea at all to go for a higher output bridge single coil - I have had a Trilogy Suite bridge paired with ‘63 Veneer Board middle and neck (‘63s are quite close to the Mother’s Milks) on Tim’s recommendation and it works really nicely. You don’t feel at all that the bridge is dominant in output, it’s just going to have a more beefier sound. A Cobra or Sinner would be even thicker/hotter, but you should still be able to keep the relative pickup output under control by height adjustment.
That said, no strat bridge single coil will sound like a humbucker. So much of the sound comes from the pickup position and angle that you’re never going to get the same effect as a traditionally placed bridge humbucker. If you truly want a humbucker sound, I think the only option is to actually install one.
Finally, is your guitar wired so that the bridge pickup has a dedicated tone control? If it has vintage wiring, where the bridge pickup only sees a volume control with no tone, I’d change that right away - just having the load of the tone pot on the bridge pickup signal will take away a considerable amount of harshness, then of course by rolling the control off a bit you’ll get the darker tone that in fact can sound a lot like a hotter pickup would.