The second idea would be crossbreeding between mobs.
I thought again about that and ... I come up with an Idea:
The main problem mentionned by Devs for cross breeding mobs is the fact mobs are laggy. That's why I thought: why no making a multi block structure, that would "suck" mobs from a door (and could also give some mobs back if you really want so), would need Wheat to run, + EU and maybe something else, but would also turn mobs into items like into a GUI (or not, it could just simply be a mob counter, but that would avoid crossbreeding and just allow [nothing here]-breeding). The GUI would makes you able to cross breeds mobs you want (just put 2 mobs into the same enclosure, and Tadaa, you'll maybe got an awesome baby animal!), but it would just be like items in a nuclear reactor.
Another feature would be makings it to generate EU (but costing Wheat, and why not a special thing that cannot be harvest by Forestry, toi makes it boring to maintain ^^) by using ... some awesome ... FECAL MATTER! Process it with any machines, and you could get Biofuel, or even Methane ! (GregTech here!).