Great idea to make if easier for individuals to enjoy the bounties of our natural wonders but I think that pesky Tenth Amendment to the Constitution may get in the way of federal government licensing.
If you somehow work it so the feds are a clearing house and each state getting a piece of the action the cost of a licence might be beyond that the average traveling angler might be willing to pay. Maybe something regional or ala carte that you can pick which states based on you travel plans. Just keep in mind no state will be willing to take a discounted or reduction of the revenue stream, no matter how small, that the current state level licensing brings in. And don't forget for every dollar the federal government distributes to the states cost .75 cents or so in administrative overhead so your costs are increasing even more for the convenience.
Plus too many city folk being elected these days at the Federal level that won't support anything other than a prohibition on the taking of ANY game nation wide and out to 200 miles off the cost. Be happy you don't need federal tags to go along with state for the game you do take considering the natural movement of critters across state lines and how the feds control interstate commerce. Maybe I shouldn't have mentioned that.