No good solution. Now, trying to "install" the designtime package, during building of the IDE, I now get "ffllexcp.pas(40,3) Fatal: Cannot find ffsrmgr used by ffllexcp, incompatible ppu=D:\Prog_Lazarus\svn\lazarus-ccr\components\flashfiler\packages\lib\i386-win32\ffsrmgr.ppu, package lazff2". This happens usually when packages have access to the sources of other packages. I can't get rid of it even with a clean rebuild of the IDE.
I did try to separate run and designtime units into their own folders, but failed because there are so many units, and I don't know which ones are real design units.