As all the comments on the last post pointed out, capping the base currency will destroy the player economy. Or at the very least, force the economy to shift to something more liquid, like cloth or barter.
So then, is it better for MMOs to avoid using the base currency for features?
I think the TOR experience this past year is instructive. When TOR introduced Galactic Starfighter, it also introduced two new currencies: Fleet Requisition and Ship Requisition. You earn Requisition by doing Starfighter activities. To upgrade your ship or get new ships you spend that Requisition (or Cartel Coins, because F2P).
In contrast, when TOR introduced Strongholds, the price of a Guild Capital Ship was set at 50 million credits.
There were no complaints about pricing for Galactic Starfighter. There were tons of complaints about the price of guild ships. Would TOR have been better off introducing a new Housing Currency, and having all the costs of housing use that currency instead of the base currency?
Perhaps it would be best to avoid setting expensive prices, and just leaving the base currency for the player economy and "small" stuff. That makes all items sold by NPCs to have "affordable" prices. All features would use their own unique currency, with separate rules and caps on acquisition.