I myself am a fan of both the P-90 sound and the Mini Humbucker, and I have guitars with
both. I have not ventured to mix the two, but it doesn't sound like a bad idea.
I am also a fan of an instrument with a unique tone, so that putting a P-90 or a Mini Humbucker
into the neck position of a Telecaster also seems like an excellent combination.
In spite of that, I never really liked the sound of "Greenie..." Loved Peter Green's songs and his
playing, but prefer the sound of an unaltered Humbucker.
The only hesitation I have concerning the guitar in the picture is that the P-90 pickups you've shown
actually look like P-94 pickups. The tone is similar to P-90, but the size is like a full size hum bucker.
So that the mini won't fit where the P-94 goes, and the P-94 won't fit where the mini goes. If you
want to replace a P-94 pickup with a hum bucker, you'll need a full size one.
Players install a P-94 in the place of a full size humbucker, when they want that sound
but don't want to dig holes in a prized guitar. I don't recommend you rout out your Les Paul just
to instal a mini hum bucker. I recommend a Gibson '57 Classic plus. Excellent tone and no
surgery.