Trading Flowers, for the Chiefs, is a net cap gain of 3.5 M. Obviously there are no problems with KC trading him. If you can trade him straight up for Revis, I think you do it... contingent upon Revis re-signing to a longer deal that makes sense for KC. Revis would transfer over his salary portion of 13 M, so that has to come down substantially. Ideally, you don't want to lose anything in year one of the trade if possible, but trying to get Revis to sign for the first year in the neighborhood for 3.5 M is tough. Realistically, I think you can look in the neighborhood of what Carlos Rogers got in 2012 plus a bit to be able to do it.
I'm thinking 4 years, 34 million, with 16 million total guaranteed, including a 7 million dollar signing bonus and the first two years salary fully guaranteed. This averages $8.5 M/year (better than L. Webb got from Baltimore in 2013). That gives you an approximate breakout like this:
Year 1: Cap = 4.75 M, Signing Bonus = 1.75 M, Guaranteed Salary = 3.00 M, Total Guaranteed = 4.75 M
Year 2: Cap = 7.75 M, Signing Bonus = 1.75 M, Guaranteed Salary = 6.00 M, Total Guaranteed = 7.75 M
Year 3: Cap = 9.75 M, Signing Bonus = 1.75 M, Guaranteed Salary = 0.00 M, Total Guaranteed = 1.75 M
Year 4: Cap = 11.75 M, Signing Bonus = 1.75 M, Guaranteed Salary = 0.000 M, Total Guaranteed = 1.75 M
Not sure if it would work, but I sure could live with getting Revis for Flowers and only spending 1.25 M more against the cap. The Bucs would save nearly 8 M.