I have mixed feelings about it. Roaming Pokemon are a pain for sure, but they provide a unique challenge to track down. Still I was very happy on Crystal when Suicune (my favorite legendary) could be battled normally. However, tracking down roamers can be fun, and always rewarding.
I think it would be cool to have this in future games: I could also see it implemented in a place like the Safari Zone (on a smaller scale) as a means of tracking down rare Pokemon in a time limit.