In a game I am currently playing, when I try to use the send constructor feature for star bases, it tells me, (dialogue box), that I can not build constructors at this time. I am pretty sure this is because I obsoleted the core game constructor in favor of my custom constructor. 

They should not let you obsolete the core constructor if it breaks the game in any way, or at least it should warn you.

It just occurred to me that it might auto-build another one if I research a better engine tech. I have been stuck on Ion engines for quite a while. 

Anyway, be aware that if you obsolete the core constructor, you can no longer send constructors, and there is no way to un-obsolete a ship. Trust me, you can't build one that is acceptable to the game as a "stock ship".

As for other stuff, the game is playing nicely, and I have not felt too hindered by the specialized techs. I have traded for a few of them but I need to make notes on the ones that I have already picked so I don't shut myself out on the choices I haven't researched yet. 

I do not like the long interval between trades. It has taken a lot of fun out of the game for me. For one thing, more often than not, when the time elapses, the AI will contact me with some dumb trade request when I am right in the middle of something more important, and that resets the time so I can't contact them for another 20 turns. The restrictions, (if there must be restrictions ),  should be half as long, and the AI contacting me should not count.

BTW, Stardock, Frogboy, Paul, anybody, please stop the damned Iconians from ding-donging me every 10-15 turns about non-existent or incidental border violations when we have a freaking open borders treaty anyway. Apparently they do this whenever there is a common border. God help me if I had a common border with all the AI.

Other than the above irritants, all is well for me with beta 6.