Back to the castle subject I think I could like this but what I'd like to see are a series of quite expensive upgrades, as it give me something to spend all my money on.
Aside from standard things like a workbench and a ammo press and a hotplate for campfire stuff and of course storage cabinets. It be nice to have things like a water purifier which is required for the green house,(which grows a series of wasteland plants for harvesting). A trophy room which contains mannequins you can store equipment on,(which then wear the equipment). An autodoc to heal your wounds, repair your limbs and cure addiction. Defenses like auto turrets and robot patrols, which can start as Protecterons then be upgraded to Mr. Gutsy's then finally to Sentry Bots.
Exactly,player housing in New Vegas doesn't offer much things to do.But a castle/estate like 'Battlehorn' would offer it's mini quests like hiring guards,a shooting range maybe, where we can practise or watch our guards practise,buying kitchen area and a cook so our guards would gather and eat at the dining hall,an upgradeable casino room where we can gamble with our servants,or a secret room,tunnel which will offer a different area(like an ancient altar,maybe a harem with slaves :teehee: ) where we can stuff our unique evil looking melee weapons etc so we would have another reason to visit our estate.
And adding gabriel77dan's new options/ideas would definitely help the DLC..I think a mansion like in the 'point lookout' would be nice http://fallout.wikia.com/wiki/Calvert_Mansion