by Ponton
I didn't read all of your post, only replying to the first part:You're right, with a little work, you can get any card back on top if it was at the bottom of the stack - with a simple, but yet detrimental difference for the player forming a strategy around such a card:
As it is now, the player wanting to harm another one by dumping "his" building needs to do work himself, wasting (maybe) precious actions to prevent a building from showing up. Whenever he harms the other player, the latter can visit the Marketplace himself and "correct" the harm. So, you can only harm another player if you visit the Marketplace just before the end of the round that is right before a special building gets built (or otherwise, you need to block the Marketplace for long enough). This is always work for the offender.
Now, with the variant of dumping buildings to the bottom of the stack, the offender needs only one action to destroy the plans of another player. This other player would need a lot more actions to get the building up again - and then the offender can strike him hard again. All the strategy basing special buildings would lose their purpose. It simply wouldn't be worth it playing towards them. In the end, it comes down to who gets more lucky and whose strategy fits the randomly built special building the most.
With the variant of removing special buildings entirely, it becomes even worse.
Of course, may everyone play as he likes, I'm just posting to prevent new players without any experience of trying this out without really understanding what's behind it. People tend to do stupid stuff like this and then blame the game. I do not want to convince anyone of you to not do this. Do it if you like. It would be no fun for me and completely against the purpose of special buildings. To each his own. ;)
Edit: now read the rest of your post