OMAHA — A roughly $300 million donor-funded plan is poised to reshape a 12-block recreational and athletic corridor on the east side of Creighton University — further meshing the private institution into the downtown of Nebraska’s largest city. Construction on some elements, including the softball competition field, baseball practice field and Sports Performance Center, have already started. Noddle, whose company also was master developer of Aksarben Village, said the goal is a seamless connection that blurs the line between Creighton and downtown Omaha. Creighton leaders expect the new Student Fitness Center and upgrades to the Rasmussen Center to further build fitness, intramurals and club sports programs. This year, Creighton added six premier club sports, women’s and men’s programs for ice hockey, golf and lacrosse.