The main problem with abolishing roaming charges altogether would be that networks need to provide foreign operators free access to their network. For example, imagine if the EU forced tram services to freely accept passengers with valid 7+ day tickets of any foreign EU tram operator.
In my opinion, the roaming charges should be something like as follows:
[li]Incoming calls: Max 5c/min.
[/li][li]Outgoing calls to any destination: Current tariff + max 5c/min.
[/li][li]Outgoing SMS: Current tariff.
[/li][li]Data: Max 2c/MB.
For incoming and outgoing calls, 5c/min should be more than enough to cover the network cost providing this service to visitors. SMS messages cost practically nothing for the operator to provide, so they shouldn’t cost anything more.
The current data charges are a total rip-off, especially with the capacity available on 4G. I believe operators are mainly charging these crazy rates to catch people out making VoIP calls (over Skype, Viber, Whatsapp, etc.)