Ballard Center Station
Originally Ballard was going to be served by a bridge over the Ship Canal along 14th or 15th Ave NW with a station along on that street. Either way such station would be far from the old town or the current center of Ballard along Market Street. While 3 stations were proposed for West Seattle, now that a tunnel is preferred, Sound Transit should consider another station further west and closer to the center of Ballard. This station may even be a surface or very shallow station. It could be designed as the last station on the line or allow for an extension along 24th Ave NW with the ultimate goal to connect back to the 1 Line further north.
Sound Transit should also consider how an east/west line towards Fremont and UW could connect to the Ballard station. If such connection could be made south of the Ballard station and if it would also include a crossover, then trains coming from UW could either turn around and head back or continue towards downtown.

One possible route would go one block further north parallel to Market Street on NW 56th St. and stop at the Ballard Library. A second station could serve the brewery district on 14th (or 15th) Ave NW. A UW line (thin line) could join from Leary Way.

Another possible route would go closer to the old town along Leary Way NW with a single station close to Market Street. A UW line (thin line) could add another station close to Fred Meyer.

Either way, the line would need dive not only under the Ship Canal, but also avoid the stormwater and sewage tunnel north of the canal which extends up to 120 feet below the surface.
It seems a single station along 15th Ave, or even worse 14th Ave, would not be enough to serve Ballard. In particular, if Sound Transit decides to truncate the Ballard line for now, it should consider a station closer to the heart of Ballard at a later time.