I believe you could do something like you propose with the current BackupPC by setting the "IncrPeriod' to 0.04 (1/24 of a day). You'd have to make some interesting settings for "FillCycle" and "FullKeepCnt" to make it keep a usable schedule, but you could then have 'hourly' incrementals.
As Les Mikesell just pointed out, the downside would be that for large instances, you'd be doing a lot of fairly expensive (compute time) operations every hour to scan the file system for changes.
I believe that FS snapshots are faster, and more efficient than BackupPC could ever be for this.
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Ray Frush