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That's a VERY GOOD IDEA, OP!
But I believe casinos with sports-betting services will NEVER implement automated cashouts for in-play betting, although there might already bots built for it, especially for arbitrage betting. BUT you could get banned for using them because you will get a higher than the average amount of edge than the casino. Read their terms and conditions.
I share your opinion on this. While it is good feature for the customer,it is not so good for the casino. That feature could decline casino's profit so that is why I think there is not big chance that tery will implement feature like this.
As for using bots, I doubt any casino allows that, but sonce I never used any kind of bot I never interested myself if they ban in case of bot detection.
Plus it will not be actual betting, but more like trading which smarter and more skillful people could consistently take profit more than the average bettor in casino. BUT it's probably a better idea for Betting Exchanges to execute OP's suggestion because Betting Exchanges because they don't take any risk. Bookmakers have their own capital, which I believe can be significant.
Betting Exchanges might actually encourage automation because revenues through commissions might be collected faster.