Do you think L3 networks are necessary?
Current projects advertising themselves as "L3s" are basically "sidechains with a 2-way peg of a sidechain token".
This can have some benefits. For example, let's say in the future billions of people use a particular cryptocurrency like BTC or ETH. We would need several L2s for this currency to be able to be used with reasonable throughput and fees by such a high number of people. A L3 could then offer 2-way-pegs for several L2 currencies and make it easier to interact with counterparties using other L2s.
I however generally see more potential for Lightning as a L3. Lightning could route payments between different channels opened on different L2 blockchains and thus provide the same benefit than a "sidechain L3", additionally bringing more privacy, instant payments and no dependency on a sidechain consensus (which may not be infallible). The only thing it needs are exchange nodes working with atomic swaps. Taproot Assets (ex Taro) for example has such a feature.
Pascalcoin's (PASC) "Safe Box" mechanism already solves Blockchain's scaling issues. This eliminates the need to build additional layers. If developers from other projects used this tech, all of our problems would be solved.
I hadn't heard about that tech and looked now briefly into it. I think it does not solve the issue. It seems to be simply a "mini-blockchain" coin similar to Kaspa or Cryptonite, where not all blocks are stored forever but basically the UTXO set is periodically exchanged between all nodes. This solves only the problem of storage but not the problem of transaction propagation and verification, and storage is not exactly the most urgent problem when we "scale" a blockchain.
L2s do solve this problem because not all nodes have to verify all transactions, and L3s could help too a bit.
However, I think most of current "L3s" are simply scams with completely awkward tokenomics.