The biggest problem I see is restrictions on budget and the amount of one type of object you can set down, however already said. lol
Another thing I would like to see is an object flip tool for a symmetric objects like the stair cases it can cause problems when you are trying to make some objects symmetric.
A better save format so that objects wont move, for instance I have found that when I place an object at lets say a 30 snap save the map go back set it back to 30 and grab the object it will move slightly(usually tilted). So I can spend forever setting an object exactly where I want it save it and it moves it off sets the look of my maps I can make it look very clean and nice save it go back to my map then everything is moved, tilted, raised, lowered, and it can even start to z fighting when I had clearly set them so they wouldn't. This could also be due to object coordinance I'll place an object at half of a coordinate or even half of that half. Either way it is clearly very terrible for maps.
Dominant object render tool, this would be when you have 2 objects overlaying and they start Z fighting while the game tries to render them both at the same time. Instead it would chose to render the dominant object over the other object allowing for a very nice clean look. This could be on a simple dominant object vs regular object vs submissive object or a scale of 1-10 for the importance of visibility of said object for multiple overlaying objects. This would be perfect for aesthetics and could possibly help with frame lag also.
Object glass replace tool, there are a lot of objects that have glass on them which can create frame lag due to rendering I think it looks very nice however at times it can be bad so maybe have a tool where it would replace the glass on an object with just a steal look for better rendering.