hmm- why can't a person simply setup their mining hardware to seek out the 1st transaction and submit it as a complete block with just the 1 trx immediately upon receipt?
Doesn't probability of finding an accurate block increase substantially as the # of transactions goes down?
No it does not increase the chances of finding a block that has a low enough hash as the number of TX goes down. It will take a little bit more time to broadcast the found block to the network as the block will be larger then it otherwise would be.
Miners have incentives to include TXs in found blocks via TX fees that make up for the larger block size