The correct answer is D. Incorporating forward-looking factors and idiosyncratic risk exposures into stressed operational loss estimates is the most appropriate process for a bank's capital planning process as per the Federal Reserve's guidelines. This is because banks with stronger practices will include these factors in their stress scenarios to better account for potential future losses and risks that are unique to the bank's operations.

Option A is incorrect because operational risks typically have a low correlation with market risk variables. Assuming a high positive correlation would not be a conservative or acceptable practice. Banks can provide correlation estimates if they have a proper defense, but a strong correlation is a cause for concern.

Option B is considered a weaker practice because combining two different models can introduce unexpected jumps in estimated losses over the planning horizon. The paper also highlights difficulties with roll-rate models, which can lead to poor predictive power for longer time horizons.

Option C is also a weak practice as it ignores potential seasonal patterns. A better approach would be to provide a careful estimate of the expected quarterly path of losses, as well as net revenues and capital projections, rather than evenly distributing the losses across the year.