My instinct is that 我要明天看电视 is more likely to be understood as "I'm going to watch TV tomorrow", whereas 我明天要看电视 is more likely to be understood as "I want to watch TV tomorrow." Can a native speaker confirm or reject this idea?
I think it comes down the idea that Chinese tends to denote time by using a time phrase before a verb. So, if "要" comes first in the verb phrase, the listener is likely to interpret it as denoting something about time, specifically, future tense. Then, "明天" is likely to be understood as just more specification as to when in the future I am going to watch TV. Conversely, if "明天” comes before "要“， I would expect the listener to interpret "明天” as the time context, and 要 to take its more literal meaning of "want", yielding "tomorrow, I'll want to watch TV.", or "I want to watch TV tomorrow."