Questions on player permissions

[blueblue]

Here are three questions that recently came up while I was trying to make a mod. The first two deal with player permissions (although not in the api sense since those are too limited), the third with gui.

I'm trying to make a player unable to build entities but still able to build blueprints and ghosts. I got it working using the on_entity_built event by destroying the entity and returning the item to the player cursor. But it's ugly because the placement effect (dust cloud) keeps appearing. Is there a better way? Also this is while the player is in god-mode i.e. while there is no player character.

I would also like the player to be unable to pick up items from chests, belts and assemblers but still manage blueprints in his inventory and view chest and assembler inventory. I am unsure if this is going to end up in the final mod so it has low priority for me but I would like to test it at least. But I just cant figure out a way to do this.

Lastly I need to make some ui in which the player can choose between different items, essentially like the signals menu or the crafting menu. Does anyone know a mod that allows to do that so I can see an implementation?