I'm not a big fan of versi tips, BUT, if you want to do the one fly line/one spool approach, a loop to loop setup with running line and shooting heads is super versatile and effective.
You could take a floating, intermediate, and very fast shooting head, and be pretty much equipped for most situations (I use old school LC-13 on my 10 weight when I'm in Mexico, but that's in deeper water, and my 10 weight absolutely launches 30' of Lc-13. You could use T-11 or T-14, depending on your rod, in lieu of the LC-13). If you're inshore (say, after trevally), the floating and intermediate heads would be your tools of choice, depending on the depth of the the water. In the deeper offshore water, where you will find the dorado, the faster sinking head will likely be (in my opinion) the most effective.
Remember, saltwater is much more buoyant than fresh water and, for dorado, you'll probably be stripping line quickly, so the fly will likely be up in the top, oh, 3-4 feet of the water column. The nice thing about shooting heads, as well, is you can take a number of them as backups, and they are much less costly than a full line.
With that said, I take an extra spool or two with me for my 10 weight. It is setup with a backup running line so, in the event I lose the other one, I can grab the extra spool and an extra shooting head and be back in the game with minimal down time.
Again, this is my $0.02, and what has worked and does work for me.