Although the young women cannot register as members of LDS crews, the crews can plan activities in the co-ed spirit. This could include high adventure outings. (Note the restrictions on overnight participation, however.) Or it might include regular mutual activities such as cooperating for an ethical controversy or ethics form, or putting on a senior ball (kind of hard with just young men). In this way, the Venturing experience can be extended to the young women indirectly, and they can contribute to the Venturing experience of the young men.
In addition, it should be emphasized that the prohibition of young women joining LDS crews is very specifically limited to Church sponsorship of crews with young women. Community crews should be encouraged to recruit LDS young women (as well as young men). In areas where young women (or young men) feel like their mutual experiences through the Church are not providing all of the experience that they desire, then perhaps community crews could be sponsored that will allow additional growth experiences for these youth outside and as supplements to the Church programs. In particular, service oriented crews and high adventure specialty seem as though they might have a strong appeal.