Can I ask why you want to have this? Is it just because it is annoying (I find it a bit annoying sometimes), or are you trying to save disk space?
If you are using the JTV recording format, both programs will be saved in the same unique sub-directory, which will be created for the Pregame. MC will then share the JTV file set components between the two recordings, so there is no extra disk space used. MC will also use the one tuner for both recordings. The two programs will be correctly and separately identified in MC, and you can easily delete one or the other with affecting the second program.
If it is just the annoyance factor, then setting one rule for the Pregames and one for the Actual Game so you can set different padding for each is probably the best solution.
Otherwise you would need rules-based Padding Times, which might be as complex as the Recording Rules themselves. Also, if you reduce the end padding on an earlier program because you are going to record the one immediately following, then the earlier program starts late, you could end up with the situation where the end of the first recording is lost, but it is at the beginning of the next recording. That is the situation padding is trying to avoid with consecutive programs.
I just go for overkill, with padding on each recording. But then if I want to keep the program for a while I'll convert my JTV to TS and trim the beginning and the end of the recording to free up disk space. It works for me.