Think about the loads that will be put on the winch you won't always be doing a pull straightforard. That is why they mount them on a plate. Its all about engineering. I would think that you may loose the structural integrity if you only maounted to the frame and might actually stress it or bend it. You have to make some sacrifice everytime you mod a Jeep and yes I understand the loss of clearance is an issue. May want to just invest in some 1" boomerang shackles to help out and that would be the max to overcome loss of lift for the weight.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184