There are lots of large games made with small crews. Just need to find the right people who have lots of talent and desire. You could save some time and cash by using MP assets as placeholders. Also, check out the MP for plugins like Dungeon Architect… Get something in a semi working state and go for a kickstarter to help fill the void asset wise. Contractors if you have the cash will help… Get a lead that will keep the team on track and within scope.
Good luck!
teak