I prefer v1-1.
Tempo changes exist in lots of music, including heavy metal. I guess your drummer wants to keep things simple. Still, it's a bit surprising he wouldn't be ready to accept the idea of a tempo change if he's in a band like yours (and capable as a drummer who plays such music). If I were in your shoes I'd probably be a bit annoyed too.
If you want to edit the song to make it fit one tempo, and that tempo is a bit too fast for parts you've written in the slower tempo, you have to rewrite the faster riffs so they don't tax your arms as much (or sound sloppy, or too busy). That might mean dropping some triplet chugging in favor of something simpler (8th notes maybe...and perhaps compensate for the change in aggression by doing all downstrokes/muting?) Or changing some 8th note chug parts to quarter note chugs. Or just rethinking the parts for the different tempo. After all it's about what really "fits" for the intent you were after. It might not be as simple as "dropping a few chugged notes".