It wouldn't be smart to believe Red Bull does not put restrictions in. That even happens inside works teams lilke Ferrari and Mercedes, where the aero/chassis departments and engine departments put together the various benefits and disadvantages of certain engine upgrades, looking if a certain increase in bodywork bulkness is worth the aero loss compared to the PU performance gain.
There will not be a free pass for Honda to do whatever it wants. The question will rather be how well these 2 companies can work together and work towards the common goal of overall performance.
For instance for the 2014 season Mercedes ditched rather late in the development the ordinary exhaust manifold for a much more compact log exhaust (which supposedly had a slight loss of power) which brought more aerodynamic performance to the table (because of better packaging). But, throughout the years they also increased the airbox intake as the extra PU performance outweighted the downforce loss of the rear wing.