1. What would be the incentive for the bot developers to adhere to a standard that would basically encourage a user to download a meta bot rather than the bot developer's own bot? Especially once they have spent significant resources to develop and enhance their bot before any standards were in place. This would require refactoring at a level that a bot developer might not want to do. The meta bot might lose out on using such a bot, which might be really good at what it does.
2. Let's consider that once bots are created a meta-bot might be able to use the bot's NLP interface to issue queries. The response format might be so varied among the bots that the meta-bot would essentially need to allow a complete pass-through of the response. This would limit the meta-bot's ability to layer on better structure on the response or even perform it's own AI layering on top of it because the meta-bot would then need to be able to parse all these varied responses.
3. How would a meta-bot rank bots in the same domain? Maybe by scraping the review ratings on multiple BOT marketplaces, gathering performance metrics by issuing sample queries, etc. Once users start using the meta-bot there is lot of information the meta-bot can gather to influence it's ranking but the issue of cold ranking BOTs is very challenging.
4. Structuring NLP queries specific to BOTs will also be challenging because the meta-bot will need to keep track of various "flavors" of queries a BOT understands. e.g. 2 hotel booking BOTs could have been developed where one does a progressive Q&A to get to information it needs to make a booking where as another understands a specific command like "Buy 2 economy class tickets from San Francisco to San Diego for 15th May"
There are other such questions that make creating a meta-bot challenging.