The Rangers are probably my second favorite professional sports team behind the Mavericks, but I usually only make one or two games a year. I try to make a game or two during April before it starts to warm up, but once June rolls around I pretty much don't even think about going to games. It is just so much easier and comfortable to watch at home. Paying for parking, walking into the stadium, sitting in 90+ degree heat, dealing with traffic leaving, etc. Just not really worth it for me. I think having the option of indoor games will benefit the rangers and definitely increase the probability of me going to games.
However, I think having the team in downtown Dallas would be a much much better fan experience. (Might not be as profitable for the Rangers due to parking revenue, though). Downtown ballparks are just a much more enjoyable baseball experience IMO. Having the option of riding the TRE, trolley, or DART in and out of downtown would be great. There are way more places to park which would decrease parking costs for a lot of fans. I know downtown Dallas is not an oasis of bars and restaurants but it would be much better than Arlington. However, as a Dallas taxpayer I do not really want to be wasting tax dollars on a stadium. I will let another city handle that.
IMO having the stadium in or near downtown Fort Worth would be the absolute best case scenario in terms of fan experience, but I doubt that happens.