I'm thinking out loud here. How easy would it be for am asic manufacturer to produce an asic that does transaction validation?
It would not need to be anywhere near as powerful as the mining asics. So I assume it could just be a USB stick.
TX validation (needed also for block validation) will be one of the future bottlenecks. But rather than needing to buy massive servers - what if a $100 USB stick could do the same?