The most likely scenario is Choo leading off for this team, taking the role of what was going to be Leonys Martin. The young outfielder has struggled in winter ball and in Choo, they would get a veteran bat to set the table. He's patient. He gets on base. And he sets a tone. Seems right to lead off the Rangers' lineup. So if Choo does, in fact, lead off, how might the lineup look? Here's one possibility:
Check out the balance in that lineup, which would make it difficult for opposing managers late in games. I put Profar at the bottom because he can get on base and help turn the lineup over, but if Martin starts hitting, he could go there too.
I didn't give Rios or Choo a set position because both have played the corner spots. It could be as simple as seeing where each is comfortable. Choo has played a lot more right field than left in his career (when not in center), but Rios is more comfortable in right. We'll see.
So what if Martin lights it up at spring training and appears ready to handle the leadoff spot? What about this option:
CF Leonys Martin
SS Elvis Andrus
3B Adrian Beltre
1B Prince Fielder
LF/RF Shin-Soo Choo
LF/RF Alex Rios
C Geovany Soto
DH Mitch Moreland
2B Jurickson Profar
You could also put Choo third and Beltre fifth. Like I said, plenty of options.
I still think Choo as the leadoff hitter makes the most sense, but he brings the attributes the Rangers wanted on offense to help them go about producing more runs on a consistent basis. He can be a tone-setter, which wouldn't hurt Fielder and Beltre in the middle of that lineup.