Now we need two transactions: first to open a channel and second to close it. We can get rid of it if all transactions will be transmitted to the network. These transactions will have low sequence number (RBF enabled) and will have lock time in the future. Instead of opening the channel, Alice will send her transaction to Bob. She will be sure that no miner will include it before locktime. When Bob will see a transaction from Alice in mempool, he can send it to Charlie in the same way. Then, we will see a chain of such transactions in mempool: Alice->Bob->Charlie. All of these transactions will have RBF enabled, so Alice can create transaction sending her coins directly to Charlie (given these two transactions as a proof any miner can see it is not a double-spending attempt and accept such replacement). She has incentive to do that, because all such transactions have to contain at least minimal fee 1 satoshi/byte to be relayed over the network. One combined transaction always will be smaller than two separate transactions, so Alice can set a bit higher fee and still get some satoshi as a reward. Miners will also have incentive to accept that, because in this way they can include more transactions in the same block getting a bit higher satoshi per byte reward.

As a result, we can reduce everything into one transaction, sending all funds to all parties. I also thought about reducing it to zero transactions, but miners probably would still want to get some fee for accepting transaction replacements and that is why at least one transaction would be necessary. This idea also eliminates the need for being online 24/7 and creating watchtowers, as all channels' state will be publicly available.