they can have pegged stable coin to pegged mcents
This can happen only if all the channels are opened using the colored bitcoin. This isn't the case with Lightning, but a sub-network could become a thing if needed, wherein sub-nodes route and make transactions with other sub-nodes, using the colored bitcoin as a unit (in this case, USDT).
it doesnt need bitcoin. LN never has.
LN has no consensus thus anything can happen. LN could build anything without touching bitcoin
but i am laughing that you suddenly want to call LN a subnet when its bridged to a blockchain you dont want to use in LN
anyway.
LN has too many liquidity leaks, bottleneck flaws. multiple ways to abuse the system. its been done many times even by the LN devs.
so i dont see why anyone would try to bridge LN to anything unless LN tries to fix its flaws.
more likely a completely different network would be created that bridges to bitcoin and other networks including a stablecoin(dusnt have to specifically be tether)
im surprised blackhatcoiner has not idolised his influencer devs hard enough to be advertising the hyperledger project of CBDC