I'm not sure I'd call it 'subjective' or 'pre-conditioned'. Traditionally, ensuring the absence of arbitrage is a guiding principle for pricing, while the risk-neutral measure is most frequently used for theoretical results. Assuming you'll be using your forecasting for trading activities, using AoA to determine price is the right way to go. Consider ...


As you said, $B$ is the lag or backward shift operator such that $BX_t=X_{t-1}$ and $B^pX_t=X_{t-p}$. Let $A$ now be polynomial, say $A(x)=a_1 x + a_2x^2+...+a_px^p$. Then, \begin{align} A(B) X_t &= \left( a_1 B + a_2B^2+...+a_pB^p\right) X_t \\ &=a_1 X_{t-1} + a_2 X_{t-2} + ... + a_p X_{t-p} \end{align} and \begin{align} \big(1-A\big)(B) X_t &=...


Chapter 2 of the Applied Quantitative Methods for Trading and Investment may be useful. You can download the excel file from the companion website. Here is the link and the Download link is at the bottom: https://www.wiley.com/en-gb/Applied+Quantitative+Methods+for+Trading+and+Investment-p-9780470871348

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