There’s been a bit of discussion about the two attribute upgrade schemes tried so far, each of which has pros and cons. The earlier random roll scheme drew some complaints and was susceptible to save scumming; the new fixed upgrades have drawn some complaints due to favoured attributes being limited to +2.
Another option that gives players a bit more flexibility in building their brothers might be to fix the upgrades to +4 for the first chosen attribute, +3 for the second and +2 for the third. This would allow more specialised builds (but retains the necessary balance that specialising in one area requires sacrifices in other areas).