Presently Interstate 4 in Florida is the lowest east-west Interstate route number in the 48 contiguous United States. Now that AASHTO has given their blessing (with the concurrence of FHWA and TxDOT (Texas Transportation Commission)), Texas will soon be home to the lowest east-west Interstate route number in the United States, Interstate 2.
As a suggestion, here is what I would do with a new Interstate 2 in the Rio Grande Valley, which I understand will replace US 83 as it is Interstate standard and being the terminuses of Interstate 69:
1. Extend Interstate 2 west to Laredo and let it connect with Interstate 35. At the same time, extend Interstate 35 south to let it become a free flowing Interstate highway straight to the international bridge and to Mexico, much like Interstate 5 in San Ysidro. Presently Interstate 35 ends in Laredo at Victoria Street (south of Victoria Street, southbound from Interstate 35 is Santa Ursula Avenue and northbound to Interstate 35 is San Dario Avenue) and motorists wanting to head south into Nuevo Laredo and points south in Mexico (i.e., Monterrey) have to go through a couple of traffic signals on Santa Ursula to get to the international bridge.
2. After Laredo, extend Interstate 2 further west to Del Rio, passing by Eagle Pass on the way. From Eagle Pass to Del Rio use the right of way of US 277. Interstate 2 would go around Del Rio using TX Loop 79 in order to meet US 90 northwest of Del Rio.
3. After Del Rio, extend Interstate 2 yet further west using the right of way of US 90 to Van Horn and Interstate 10.
The only acquisition of right of way in my suggestion would be for the segment of Interstate 2 from Laredo west to Eagle Pass. That way, right of way acquisition costs can be held down and TxDOT - known for the frontage roads on their Interstate highways - can construct frontage roads on US 277 and US 90 through the more populous areas in order to keep existing roadside businesses going.
I would welcome the Interstate 2 idea for the Rio Grande Valley area of Texas, as long as if there were plans to extend the highway westward towards an eventual connection with Interstate 10 at Van Horn to El Paso and points west.