Dave:
here's one proposed workflow. lets assume we only do this for payment processors like PayPal Web Payment Pro, Authorize.net or Moneris (where u can collect credit card and send over a request/get response etc)
1. introduce option to enable "real-time" contrib in offline contribution page and payment processor to be used
2. if enabled add credit card fields and billing info fields to form
3. in postProcess make the right calls (the code is there already) to process the contrib
We reuse a lot of the code we already have, we continue our policy of NOT storing credit cards in DB and we implement a useful feature

If this is super important, we could potentially get this in the 1.8 release (code freeze is 10 days away). I suspect this will take between 30-50 hours to make it generic and integrated etc. We can chat on IRC with regard to more details.
lobo