Alright, so I guess this is indeed not doable out of the box.  I've
implemented this on my fork of org-mode:
   https://code.orgmode.org/michaelcadilhac/org-mode
(Also two more things that may be of interest: Include tags in summaries,
and give a bit more information about the timezone—ical.js does not
recognize X-WR-TIMEZONE.)

Hopefully this will be useful for someone :-)

Cheers;
M.

On Fri, 1 Feb 2019 at 12:47, Michaël Cadilhac <michael@cadilhac.name> wrote:

> Hi there yall;
>
> I use org-icalendar to export my TODOs and events to an ics, that is then
> imported in Google Calendar.  As far as I can see, Google Calendar still
> doesn't support VTODOs, so only the VEVENTs are relevant.  *My goal is to
> have my day on Google Calendar looks like my Org Agenda; *in particular
> this means:
>
> 1.   I want my repeats to appear today.
>
> To do this, I have to artificially bump the timestamp of the VEVENTs that
> correspond to a not-DONE TODO to today (and maybe add the "72x" indicating
> that the TODO was scheduled 72 days ago).  How can I do that?
>
> I believe this is not doable out of the box and that I'll have to
> modify org-icalendar-entry; is that correct?
>
> 2.   I want my DEADLINEs to show up `org-deadline-warning-days` days
> before in the export.
>
> Again this means that I have to artificially change the date of the VEVENT
> (and maybe add the "in 6d.").  How can I do that?
>
> Thanks very much!
>
> Cheers;
> M.
>