Tapu Lele would be better for that team
Mawile-Mega and Tapu Lele form a nice offensive core, taking care of each others common checks easily. Mawile-Mega appreciates Tapu Lele's ability to beat Venusaur-Mega, Rotom-Wash, Toxapex and Skarmory, and Tapu Lele appreciates Mawile-Mega taking care of Heatran.
Greninja-Ash + Tapu Lele is also very effective, as Lele takes care of bulky Water-types such as Toxapex, Gastrodon and Tapu Fini, and other Greninja checks such as Tangrowth. Greninja, in return, can kill Heatran and other Steel-'s for the Lele. Greninja can also lay down Spikes for the Lele to break late-game, and Lele appreciates VoltTurn support a lot, so Greninja, with the number of switches it can force, can bring Lele in safely. Greninja-Ash can also decimate offensive teams once Tapu Lele is done with the wallbreaking.
Kartana also does the same thing, it can pressurise Steel-types for Lele, and Lele can take on its checks easily.
If we compare Tapu Lele and Jirachi, though, you'll find that Lele has much more offensive prowess, and as this is an HO build, Lele would be a far better option than Jirachi, which, comparatively, is better on BO and Balance builds.
That's all, hope it helped!
