Kurumiru (hopefully not more than 2-3) could have gone to further developp other pokémon, get more out of them, maybe get them a new moves.
That might very well happen. That doesn't mean I have to agree with their choice for that 7th pokémon, when pretty much eveything it could contribute to Ash's team, Snivy could already bring. The League all to themselves argument makes sense, but why not give Ash pokémon with more diversity, more different battling styles... As I said before, if Tepig evolves, Ash will have two fighting types and two grass types on his team. Should he catch Sandile, he'll have 2 dark types to boot...But how do you know you won't be satisfied what it has done by the end of BW? What if it's screentime was just how you wanted and the writers pulled it off despite Ash rotating 7 pokemon?
2- Ash already had a Snivy that was underdevelopped and is in need of battles and screentime.
Still, the more pokémon you give Ash, the less each individual pokémon will get. I mean, after 18 BW episodes, we have Invisibird who's still looking for its personality, a boring pig, a plotless mijumaru, a Snivy with plot and personality that the writers aren't using and a Zuruggu with a plot and personality that the writers need to address. Instead of working on these guys, fleshing them out, developping their personalities, giving them individual storylines, etc, the writers are giving Ash another pokémon, who lost its personality during its capture episode, was wild and already strong, so no real plot, no real hardships, nothing to overcome.Without the main girl being a co star the writers will have a lot more time to focus on Ash's pokemon
It's blah and hopefully, will go the way of Butterfree after evolving. Did I mention I'm really hoping for quick release and never seeing it again?