I wanted to draw specific attention to that paragraph, and you should make v4.0 with that in mind, it's really important.The problem is though that instead of carefully designing each room, you make a basic container for what it should include and then paste some of your scenery eyecatchers in there at more or less random measure. Each room should look unique and carefully designed, that probably your biggest problem overall. Your approach seems to be "Let's make a room to fit my gimmick and then try to make it look good afterwards". This makes every room look similar and none of them truly unique and is what divides you from the best mappers in this community.
Also, I terribly misunderstood you. I thought the palmtrees would cause lag, but you said they cause HOMs, that's an entirely different thing.