All the features you suggested have already been part of the plugin since quite some time.
You can disguise as a falling block or item stack using the default command /disguise. Simply type /disguise and you will get a list of all disguise types available.
It is also possible to be in actual block coordinates only if you're disguised as a falling block. To enable this functionality just apply the subtype block-coordinates to your falling block disguise.
You may also read the Commands and Permissions page at dev.bukkit.org:
https://dev.bukkit.org/projects/idisguise/pages/commands-permissions
Feel free to send me a private message in case you need any further information or help.