The sexual dimorphism you are trying to avoid (size) is based primarily on the advantage that greater physical strength gives a man, allowing him better access to women than he would otherwise be able to. The strictly aesthetic differences can be explained by simple sexual selection (men like bigger breasts and women like wider shoulders).

There are about 5 mating systems: monogamy, polygyny, polyandry, polygyny and promiscuity. Polygyny and polygyny tend to favor physically stronger and larger males that will monopolize mating access to females, whether individually (polygyny) or as group (polygyny), you want to avoid those in the evolution of their hominids. Another aspect that correlates with these stronger males is sexual cohesion, where the male will physically attack or intimidate one female in another, making her more reluctant to mate with other males, this is more associated with polygyny or promiscuous mating, as it require the females to have access to multiple mates for the intimidation to result in a advantage.

Therefore, in order to minimize the gender disparity, you must focus on strict monogamy or promiscuity, with either an egalitarian or female-dominated social hierarchy to avoid sexual coersion. The strict monogamy is less likely, as it is usually not associated with mix gender groups and if extra-pair copulations occour it may favor higher status (usually the most dominant or strongest, but also those with more alliance/friends), whith may lead to the dimorphism in size. Lifestyle also plays a role as the traits associated with physical strength and size may also make them better hunters, and individuals that can bring more food to the group may be attractive for the females, which can create a quasi-harem for some males in a promiscuous systems.

Overall, there is no recipe that leads to a specific result when it comes to evolution, but my sugestion would be promiscuity with a female-preference for less treatening males, not stronger or larger than them, but keeping the general preference for masculine traits in order to keep the dimorphism in other areas.

The sexual dimorphism you are trying to avoid (size) is based primarily on the advantage that greater physical strength gives a man, allowing him better access to women than he would otherwise be able to. The strictly aesthetic differences can be explained by simple sexual selection (men like bigger breasts and women like wider shoulders).

There are about 5 mating systems: monogamy, polygyny, polyandry, polygynandry and promiscuity. Polygyny and polygynandry tend to favor physically stronger and larger males that will monopolize mating access to females, whether individually (polygyny) or as group (polygynandry), you want to avoid those in the evolution of their hominids. Another aspect that correlates with these stronger males is sexual coercion, where the male will physically attack or intimidate one female in another, making her more reluctant to mate with other males, this is more associated with polygynandry or promiscuous mating, as it require the females to have access to multiple mates for the intimidation to result in a advantage.

Therefore, in order to minimize the gender disparity, you must focus on strict monogamy or promiscuity, with either an egalitarian or female-dominated social hierarchy to avoid sexual coercion. The strict monogamy is less likely, as it is usually not associated with mix gender groups and if extra-pair copulations occur it may favor higher status (usually the most dominant or strongest, but also those with more alliance/friends), which may lead to the dimorphism in size. Lifestyle also plays a role as the traits associated with physical strength and size may also make them better hunters, and individuals that can bring more food to the group may be attractive for the females, which can create a quasi-harem for some males in a promiscuous systems.

Overall, there is no recipe that leads to a specific result when it comes to evolution, but my suggestion would be promiscuity with a female-preference for less threatening males, not stronger or larger than them, but keeping the general preference for masculine traits in order to keep the dimorphism in other areas.