He wasn't playing the part of a lineman there's no rule stating you must have 5 linemen.
Yes there is. You must have at least 7 men on the line of scrimmage at the snap (and for the purposes of this discussion, I am going to assume there are exactly 7 men on the LOS). The 5 in the middle are considered linemen. That means they may not receive a forward pass and they are not allowed to advance beyond the line of scrimmage prior to any downfield forward pass being thrown.
His position was receiver as was his number.
Vereen was not a receiver on the play in question. Note that at the snap of the ball, Vereen runs back a yard or two and fakes like he might catch the ball. It would have been illegal for Vereen to go beyond the line of scrimmage prior to the pass being thrown to Hoomanawanui. It also would have been illegal to throw a forward pass to Vereen, but there's certainly nothing illegal with him holding his hands out and yelling "I'm open!" as a fake.
The only thing that differed was that he in fact declared himself ineligible. The rule states you must have 7 players on the line of scrimmage. It doesn't specify what players they have to be.
Yes it does. It says the 5 in the middle must be linemen (ineligible) and the 2 on the outsiders must be eligible receivers.
Obviously, players who are normally ineligible can declare themselves eligible, but they have to line up as 1 of the 2 outermost guys on the LOS. Furthermore, guys who are normally eligible can declare themselves ineligible, but they have to line up within the group-of-5 men in the middle.
The new rule says a guy who is normally eligible can declare himself to be ineligible but from now on must line up in the tackle box, not split out in the slot like Vereen was.
The only eligible receivers by rule, on the line of scrimmage, are the players on each end of the line. So my question is why can't you run the same play just not declare him ineligible (since by rule he's not anyway)?
If you run the same play without Vereen declaring himself ineligible, it would be illegal. That was true before the rule change as well as now after the rule change.
What if we lined up a TE to block? As long as they don't go forward I fail to see what the difference would be.
If he was part of the "middle 5", then the TE would have to declare himself as ineligible. Under the new rule, he would also have to line up in the tackle box. If he was one of the guys on the end, then he is an eligible receiver. Obviously the fact that he is an eligible receiver doesn't mean he can't stay in tight and block. He certainly isn't
required to run a pass pattern.
Or why the Ravens defense doesn't know that the only receivers eligible on the line of scrimmage are in fact the 2 end players.
The home viewer gets a side view of the action, but I can certainly understand the logic that a guy on defense facing the line of scrimmage standing 15 yards away might have a tough time figuring out exactly who is standing on the LOS and who is 1 yard behind it.
Basic football. The reason the play isn't used so much is that you are limiting yourself to 4 linemen
The reason the play wasn't used so much is because it was a brand new innovation. It took a play the Alabama Crimson Tide ran and added a new wrinkle to it. No one had done it before or seen it before. It was Belichickian genius.