Blockbuster trade advice: good deal?

Absolutely not. Agreed with the other guy, Brown is not as good as Smith, so you won't get much there. At WR you will lose a lot. Fitz is a top 5 WR and neither Jennings or Holmes are even in the top 15(maybe give or take Jennings). Knox will probably give you the same return as Holmes too. Definitely don't do that trade.