Thank you for asking this feature.
We do have plans for Custom Dashboards. The first version of it maybe as we call it internally "Graphs Tab". This would allow you to select different metrics from different monitors and have all metrics show in one graph or one below the other as different graphs. I guess saving this in to a named "tab" would make it a custom dashboard of sorts.
We will post screenshots of it when we have some version to post here.
If you can give any checklist items that you would like to ensure is present in a "Custom Dashboard", please list it here.
Now talking about making it available with R/O access, I believe today you can provide Web Client Users a Read Only Access role and associate users to specific "Monitor Groups". They will then be able to see only those Monitor Groups and monitors present within that "Monitor Group". We will do something that works within this framework when we release this feature.
I hope this would satisfy your requirement.
We hope to have this done within the next 2 milestone releases.