Sure you might have Spain and Czechoslovakia as puppets, but Germany's research teams are much better overall (presumably) than either of those two. (Note that allies in wartime at least, and possibly peacetime, give/cheaply sell their blueprints to their other members.) Personally, I play with more than the base tech teams so I find the extra IC from those conquests provides additional research slots is more valuable than grabbing blueprints from an ally.
Also as I'm sure the relationships really don't matter between Germany and the UK/France in the long run, belligerence is in my opinion a much more important value as it determines better when and who can attack you.
Have to agree with Kannon, a high degree of central planning ends up causing more problems than it is worth (units take forever to upgrade and cost a whole lot more IC), until you get to the point where you produce units that you will never need to upgrade.
You
may encounter some difficulties with the long unit build times if you wait to start building units until 1939. Western Europe may not be a big problem, but the Soviet front may give you some difficulties. I've been playing the AAR mod for the last year and so I tend to build up a nation from 1914 or 1918, and not start just prior to the war ('33/'36/'39). In that mod I tend to start building up in mid 1936. You may want to take a look at this
http://forum.paradoxplaza.com/forum/...e-to-the-Memel AAR, it has some thoughts on Germany's buildup from a '36 start in 1.01 I think.