I'm looking for some wired client isolation on our public IPv4 VLAN. Since we've a /23 block, isolation is a kind of feature that's really useful.

But we don't have switches capable of PVLAN. To circumvent the issue and don't waste public IPv4 addresses with /30 links I've come across a solution looking through the web and I've found some information about setting up a port on a given switch to be the "uplink port" with some untagged VLANs, and on the access ports just a single VLAN.

For example:

Port 24: VLAN 100,101,102,103,104 => Untagged
Port 01: VLAN 101                 => Untagged
Port 02: VLAN 102                 => Untagged
Port 03: VLAN 103                 => Untagged
Port 04: VLAN 104                 => Untagged

Finally the question: this really works as expected? If yes how can I cascade switches using this approach?