I've had a Les Paul with humbuckers for over 30 years, so I know what humbuckers can/can't do.
My opinion is to stick with the P90's - they are a sweet pickup the 'buckers aren't the panacea that you think they are. Put your money towards a new guitar.
Do as I did and just save, until you can get another guitar it's well worth it and such a sweet reward in the end!
Just my 2 pence worth !