I wonder why the officials need to differentiate between offensive skills players. An RB can pass the ball the same as a QB, are they restricted from kicking the ball? I can see the o-line having different numbers, but I don't quite understand the differentiation between skills players.
Unlike the NCAA, the NFL has rules on who has to line up where, as far as the 7 man line. There has to be an eligible receiver on the end of the line, and it makes it easier to note who is potentially eligible. An out of sequence number can be eligible if he "reports" to the Referee prior to the play, but the league's thinking is the number scheme helps.
In the NCAA, there just has to be 5 players numbered 50-79 on the line, and while they are never eligible receivers (there's no "reporting" and these guys by rule can't catch a legal forward pass), they can be on the end of the line.
Remember, however, that the guy the widest out may appear to be on the line, but he isn't. He's a step or two off the line, or was and shifts to a position on the line. Also, this doesn't answer all of your numbering quirks, but its just the way they think. The NFL also has numbering schemes for the defense which aren't explained by what I wrote here.
I agree- I think these are old rules for a "new" style of play in the NFL. I think ALL WRs, RBs, QBs, and TEs should be allowed #00, and 2-49, and also 80-89. Offensive linemen should have #50-79. Defense can be anything. I do not believe ANY player should be #1, just for the connotations of the number. If I were a coach, I'd ban the number from being worn by my players.