The Nippon Ham Fighters are said to be interested in building their own stadium in or around the Sapporo area (fifteen to twenty locations in all) by about 2024 (twenty years since their move to Hokkaido in 2004). They believe a new stadium will help pave the path to a more productive relationship with Hokkaido and bring the organization more financial stability.
The Fighters are currently using Sapporo Dome as their home stadium. The city of Sapporo owns the stadium and Sapporo Dome Company manages and operates the facilities. It costs the organization about eight million yen in base fees a day (or about 1.3 billion yen a year). If attendance goes over 20,000, they have to pay an addition 400 yen per head.
[UPDATE 5/26 @ 4:19am]
A few more bits about the stadium plans.