I think that musing.io should use the ranking system to determine the questions or answers that their bot will upvote?

A moderation / curation team is currently a much better solution than using a bot to determine which posts musing should upvote.

There have been various attempts by different Steem platforms to use bots to determine which posts to upvote. Typically these approaches quickly suffer attack by people looking to scam the system (for example through sybil attack) and the reputation of the site suffers as a consequence.

An alternative / enhancement which could be considered is to give musing contributors a rating based on the quantity and quality of their prior posts, i.e. how much they have contributed to building the Q&A bank in the past, and then use these ratings as weights for the upvotes in determining the best answers.

This is the approach that Utopian uses. It essentially increases the size of the moderation team to trusted members of the community. However even this approach may be gamed at musing since people could quickly gain ranking here (the significant effort required to make a utopian post means this approach is harder to game at utopian).

In summary, a moderation / curation team is probably the best approach available.