On a second thought, this criteria is not good. Technically it should be possible to send a tx with any amount of outputs. And if people started feeling generous and started giving bitcoin to every existing wallet, the UTXO set will explode but that would be part of the protocol. 
Maybe another technical solution can be implemented to ease RAM requirements because of the UTXO set. Maybe in the future SSD storage will be fast enough to store everything. Only 87 M UTXOs now. Nodes should be able to handle 9 B UTXOs if btc was to be truly global.

sandbeach123

bitcoin

Bounty of 45 million for stop Ordinals on Bitcoin Core

Rsync25

If the ordinals/stamps will increase the size of the UTXO set too much, then I would prefer to soft fork my node and keep out (AKA invalid) all txs that will have say more than x outputs.

I mean, today you need at least 3-4GB of ram to run a bitcoin node.
If that requirement goes up to say 8-10 GB because of this, that will make running a node very expensive, and that will hurt decentralization. 
All I care is to keep running a bitcoin node as affordable as possible. IMHO.