Arlington City Council members seem pleased with ideas for a new, 80,000-square-foot Central Library building, meeting space and public square presented to them by the city staff.And who wouldn’t be? The 40-year-old George W. Hawkes Library just east of City Hall has significant maintenance problems and, at 63,000 square feet, isn’t large enough to provide all the services needed at a modern central library.It’s also easy to be pleased because this is only a concept. Crucial financial plans are yet to be worked out to cover its expected $26.6 million cost.The financing is expected to involve tradeoffs, such as devoting to the library some of an estimated $20 million that otherwise would go toward fixing streets.The new library and plaza would be built north of City Hall, with a separate 6,500-square-foot building that would be both a new City Council chamber and shared library meeting space.That brings up a complication. Mayor Robert Cluck and council members Robert Rivera and Charlie Parker have pointed out that having a nice, new library next door might make the 33-year-old City Hall show its age.They asked for a staff report on what kind of maintenance work is needed on City Hall and what it would take to upgrade its exterior appearance.The city staff has prepared a report for discussion at Tuesday’s afternoon council meeting saying that City Hall “is in good shape and is still very maintainable.”Still, it needs $570,000 in major maintenance in the next five years, plus $300,000 for a freight elevator and $90,000 for a new first-floor air handling system.The report gives no estimate for the cost of an exterior upgrade, but it says it should include replacing all of the windows, which are no longer energy efficient. Major work would trigger requirements for accessibility upgrades under the Americans with Disabilities Act, the report says.Finally, discussions have included possibly paying some of the new library’s cost by issuing debt without voter approval, a dicey political move.The problems of the Central Library are well known, and the proposed City Hall/Library Plaza looks like a good way of dealing with them. But tough decisions lie ahead.