It is not something that is supported currently. It would require a change to the blockchain to add the curation guild functionality.
There are a lot of implementation details that would need to be ironed out. I suspect that if they did it, the SP would be allocated to the guild unless/until the whale decided to unallocate it.
One reason would be that a good curation guild could potentially earn better curation rewards than a "dumb bot". Also, whales could support guilds that were voting on the type of content that they felt was advancing the platform - without having to acutely curate and read all of the posts themselves.
I would say bots are a lot smarter than manual curators. Most people have no idea about the 30 min rules for example. Every bots knows about it.
Also bots can upvote much faster so they always outpace manual curators. If you look at the curation rank, all the top curators are bots.
I've subscribed to biophil's bot and everytime I vote manually it reduces my score, I need to let the bot do the work if I want to keep the same curation score. The only way manual curators can earn more than bots is if a really great post from a new author is only noticed late by the community( which is very rare). Manual curators stand no chance against bots.
If curators of a guilds are bots too then whales will just chose guilds with best curation score or as you say guilds voting for specific stuff