When Seattle’s Sound Transit looked at extending Tacoma’s LINK light rail, they nixed a Tacoma Mall alignment early on, because the grades on 25th and Pacific were too steep.
Thing is, the streetcar companies figured this out 120 years ago, which is why they carved out a diagonal street to provide a low-grade route up the hill to South Tacoma. The Lincoln District formed where it did because that was where all the car lines converged to Downtown.
Similar bits and pieces exist throughout the city. Baker Street was carved out as a switchback to allow 6th Avenue cars to make it down the hill to St. Helens. 45th at Orchard was realigned for streetcars, as was Tacoma Avenue; note the still-visible trackway.
All of which is to say, if you’re considering a new rail alignment, you ought to find an old map or three and familiarize yourself with what the original system looked like. Your problems may have already been solved.
Sound Transit’s commitment to “sub area equity” ensures that as Seattle’s rail is extended to Bellevue and beyond, Tacoma will continue to see rail expansion as well. And if there is to be a train to the mall, why not take the direct route?