It's really surprising to me that a mod like this doesn't already exist (as far as my search efforts have shown). The concept is a really simple one: in career mode, when a new contract becomes available, the player is alerted about it. This allows the player never to miss out on an interesting contract opportunity (as my understanding is that offered contracts do expire after a time), or at least to know ASAP that new contracts are available. I don't know how difficult it would be to implement, but it could even probably be really nicely incorporated into existing mods like CapCom or Kerbal Alarm Clock.
Just wanted to put that idea out there!