i can't tell if your being sarcastic or not but I would agree with that if he could be at least an average lf defensively. There are a lot of big name 1 sackers out there, many of whom occupy spots on possible big market destinations already. The list of left fielders who can post the type of offensive numbers Votto is capable of is a much shorter list.
Although I wonder which position increases risk of injury more 1b or lf...my guess would be left field.
I'm serious about it. I wish he was willing to move to LF, but I think he has no reason to try if he's comfortable at first. His value could increase like you say, and like I originally thought, but it's hard to see his value much higher these days anyway. If I were Votto, I'd try LF simply because you're one step further from the door when you're older. Adam Dunn never wanted to be a 1b because, boom, now he's a 1b/DH the very next year. He'll likely struggle to get his next deal beyond 1 year 4million. Just my take on it.