Did you start with Danzig event?
I had actually made an earlier post here setting out possible timetable, but then deleted it.
I am not sure how to answer your question as I never tried it myself. But I can provide some timelines by which you can judge your "timing question" on your own.
A good attack on France (including Luxembourg, Netherlands and Belgium) is one month for Vichy Event to fire. It has been done in 10 days but that was using 5 paratroopers, and very good luck as regards the weekly check "if Vichy conditions met" having occurred right after the 25% of France provinces taken occurred. It is not usual that once victory conditions are meet, event will not fire for up to a week waiting for the check to be made (as that is done only weekly).
I believe any logical German conquest must secure the Kattegat Straits. It should be no more than 3 days for Denmark to fold her army (especially an early attack when it only has 1 or 2 divisions in Copenhagen), so allow a week extra for that including moving units as needed.
It takes about 2 months more to fix up all mentioned so far since repair at maximum is not possible given so large a conquest done so quickly. This time will see the Wehrmacht moved from France to Polish border.
A good attack on Poland is only a week (it has been done in 5 days). But allow for 2 weeks since things are much more complicated since you already have incurred concerns regarding fortifying the Atlantic Wall. Repair will be another 1 week - provided repair rate was at near maximum once Poland invasion started.
So adding that up: 1 month, 1 week, 2 months and 3 weeks = 4 moths total.
Starting September 1st 1939, it should all be finished (provincial repairs at near zero) by Dec 30th 1939.
IF YOU STARTED HISTORIC DATE, it seems that annexing Poland (with Vichy fired) by November 7th 1939 is very good. Only, did you secure the Kattegat Straits.... or are you overlooking that?
You make very well a different point: CAV-4 in 1939 simply are the best all-around unit and rightly deserve the title of "Poor Man's Armor".
So what's next.... attacking SU in June 1940; or attack soon after Stalin starts the Winter War with Finland? I would guess the latter would be best ... and your many CAV-4 will do just fine. Certainly there is little time to change them for MOTs or ARM. Suggest giving them all brigades (and about 1/3 give AT brigade to decrease their softness), and their overall slower speed will actually co-ordinate better with a mostly infantry army lacking any major mobile segment (MOTs MECH, ARM).
You may want to start thinking about a navy to take British Isles since it should be possible to get Bitter Peace sooner than it takes to build a Bismarck.
Good luck!