I do not see the point. To display anything in the client it needs to be downloaded.
Also report display data that are already encoded in the system so it is not really useful to have it next to the data input.
And finally by default the reports are in OpenDocument which are not really supported as preview.
A mix of graph and data will be great, but, in my case, to generate custom reports data I generally use dicts or dataframes, so, I would like to have a view where I can render data (using somethings like Weasyprint) inside Tryton. Instead of generate a report I can use a view.
The balance sheet already exists in Tryton as a tree view.
It is more powerful to format data as ModelStorage in Tryton because it can be reused and it integrates well.
Indeed it can be a little more work but this creates better user experience. At least that the assumption Tryton is based on.