The only way I know of that will let you do this is with virtual utxos, which means locking up an on-chain utxo and promising parts of this utxo to many people.

Ark has a solution that accomplishes this, but the ugly path is too ugly without covenants.

Covenants in general would sort of accomplish this, if you could enforce a user to spend with a particular change output. Then you could have users swap vtxos around on a layer 2, and if things get ugly, the covenant restricts everyone to exit with only their share of the utxo.

Any side chain solution is an implicit block size increase, as the total network must store more data in order to validate your holdings.

Also, lightning is not limited to HTLC payments. There may be other channel configurations worth exploring.