Certainly there are people that know better than I know but the thing about cutting and welding new metal bothers me. Maybe this is not as hard to do as I think but metal is not all the same. Even if you call this metal Steel it is unique. Even if you have a general idea as in it is Mild Steel it is unique. Even if somebody says it has 0.2 Carbon in it is is still unique. Maybe I'm getting across what my concern is. Any new metal added to the tank will not be the same and then a process of electrolysis will be set up.
Maybe this is not a big concern on motorcycle tanks? I used to work on boats and they talked about this stuff all the time. I don't understand it always but I think it's a concern.
Good luck. I'd still want the tank as originally made. Unless you change the front forks of the bike and the dents have some purpose again.
BTW, you are going to do something with it, why not strip the paint now so you can see what's ahead?