What else would we like in an older audience: a more realistic portrayal of the practicalities of warfare as well as the old 'realistic portrayal of war is hell' such as employing a cell system, having characters research warfare rather than having a inborn genius (like Marco).
Rather than having 6 child heroes and the very unrealistic 'adults are useless' it would be more realistic to have a range of characters and ages and a higher death rate. it would be wise to have each cell either equally balanced (and therefore have the adult leading) or completely monogender, mono age (to avoid the adult men sending the 'little children and defenseless women' home because they think child warfare is wrong and women shouldn't be involved in combat (as in real life armies), so instead you would have all teen girl group of 6 and an adult woman group of 6, and a adult men group of 6 and a teen boy group of 6... to counteract the monotony, of 6 similar girls failing lacking the diversity of character that was the strength of the original animorphs was that each member complimented the group (the lancer, the big guy, the brain etc). you would actively recruit members from different cultures, educational backgrounds and personalites (a girl version of Marco, an adult version of Jake, an adult woman version of Tobias, an adult version of Rachel etc, a leader, a lancer, a big guy, a smart guy a chick one for each team). A good idea would be to discover which university students were controllers (engineers make especially good terrorists according to Al-Qaeda) and seek to kidnap and de-infest them rather than free the sweet little kid with down syndrome because you are sentimental. This team would work closely with Ax. Ax would be the linchpin of these cells: they would know as little of each other as possible but only know Ax. Another point going back to Leader, Lancer, Big Guy, Smart Guy, The Chick. is that the cells (like real life armies often) would specialise: the teenage girl group might be the chick (as well as having a leader, lancer, big guy, smart guy and the chick) would specialise in seeking out new recruits with useful potential and light reconaissance, the adult woman group might focus on logistics and more difficult aspects of reconaisssnce (lancer/smart guy), the teenage boys would be involved in active aggressive combat (the big guy) whilst the adult men would lead (leading/lancer) and so on... there are so many interesting ways to fight the yeerks...
think about the huge range of people who join the army in real life and how this enriches the armed forces rather than harms. But a more rational rather than emotional approach to warfare would be good.
http://tvtropes.org/pmwiki/pmwiki.php/Main/AdultsAreUseless http://tvtropes.org/pmwiki/pmwiki.php/Main/FourGirlEnsemblehttp://tvtropes.org/pmwiki/pmwiki.php/Main/FiveManBandhttp://tvtropes.org/pmwiki/pmwiki.php/Main/CommandRoster