I guess my use case is pretty common: I use org-agenda to keep track of
appointments, and use org-agenda-skip-scheduled-if-done to avoid
displaying past appointments. If I want to review what I did last week
for instance, I'd like the SCHEDULED dates to appear in
org-agenda-log-mode, not the dates where I closed the TODO entry. But
org-agenda-log-mode-items only has support for closed, clock and state
changes. A nice feature would be a 'scheduled option, which would
display done entries that have a SCHEDULED tag.

I tried to implement it, but got stuck at date handling (apparently, the
problem is that SCHEDULED items use <> syntax, while CLOSED uses
[]. Not sure why.) Could someone take a look at it?

I'm attaching a very preliminary attempt to implement it, in case anyone
is interested. It's buggy because of the date issues.