TESLACOIL, I consider your challenge to be impossible, because there is more than one way to resolve it. Here are two ways:
The shift sequence could be "The odd prime numbers together with 1"
Or it could be "Odd squarefree numbers"
There are also other ways to generate sequences which could be used for the "HELLO" example to finish up with "CDXPN"
Both answers are correct in their own way. The pattern is this: 1, 3, 5, 7, 11. Shift the letters that many places to the right:
B + 1 = C A + 3 = D S + 5 = X I + 7 = P C + 11 = N
So, that is it for this issue's codebreaker. If anyone wants to submit something for the next issue, all submissions are welcome!