How to chose an IF, or how bad is zero-IF really?
OK you are basically proposing a zero I.F. in your question - I see that now!


I don't see op-amps as a problem (not these days) - you can get ones that are over 1GHz GBP which means at 20MHz bandwidth you could get a gain of maybe 30 to 50 (op-amp choice variations). No need to lose the lower 1MHz though and, you ought to consider some real good low pass filters to remove out of band noise. Basically filter out whatever you can that's not required and that includes some good filters on the RF signal recieved - if your bandwidth is only 20MHz in 1.4GHz, removing as much as you can from outside this area is a good idea.
Use the full base-bandwidth is my thought.
Maybe but without a brain dump or a vulcan mind meld I can't anticipate anything LOL.