My point is, if you're going to change everything, don't call it Days of Futures Past.
If you send the same character who went back in time in the comic but bend the rules of time travel to allow that, it's changing everything, but if you send a character who famously dies in the future back in time, it's not? I hardly think that's changing everything. We're still talking about an X-Men storyline involving a dystopian future, Sentinels, and traveling back in time to change that future. The details are clearly being changed either way and I don't think the exact rules of time travel are important.
Granted, it's been a long time since I saw the 90s version, but was Bishop's memories sent back in time or did he physically travel?