Why do you assume that payments channel will be closed?
The main goal of the LN atleast on the BTC side is for the LN to be kept opened.
A LN channel is a free market approach and people will open and close channel it it benifts them,
If they want to covert to onchain bitcoin to LN btc and viceversa they can use a Sub swap.
Do note you don't need a fork to scale the LN future.
Hyperloop allows 3 billion LN channels to open a year in the current state of Bitcoin with no Taproot and such(plus at bare max).
Splicing allow a individual user to close and open channel the same time in on tx.
LN factory and Statechains allows to move the LN channel creation in third and fourth layers...
Each with the pros/cons but all keeping the noncustodial nature.

I do note the dust limit attack while real can mitigated and secured with various LN tech. For one Watchtower should provide enough security to prevent fraud of dust tx.
And here are some ways to solve this issue:
https://bitcoin.stackexchange.com/questions/85650/htlcs-dont-work-for-micropayments/85694