Ambient Occlusions are basically shadows that are placed around bricks, if you have played the new version of Roblox and you have a good graphics card then you should have seen these already. Ambient Occlusions would make the bricks look better, more detailed and its just something that feels good when enabled.
Idea 1
Once Badspot has enabled Ambient Occlusions for Blockland he can make a separate lucid program that displays your Graphics Card and RAM of your graphics card in the Options menu. For Example (Nvidia GeForce GTX 550 TI 256MB, 512MB or 1GB of Ram...I have 1GB)
There in the options where it would state your graphics card, you will have settings as to enable/disable Ambient Occlusion and how much you want.
Idea 2:
Badspot makes a program that detects how much ram your graphics card has, if it has lower or equal to 256MB of ram then Ambient Occlusions will be disabled or only show if there are only x number amount of bricks. If somebodies computer is not strong enough then the Ambient Occlusion option will be disabled. If you have more ram like 512MB then the Ambient occlusion setting would be enabled but would be set to low by default.
(This option should be disabled by default just for safety)