You're assuming this is a genuine process
I'm afraid there's very little point in engaging in the phoney debate over this draft bill - that simply lends legitimacy to the process.
There is no intent to change existing practice, the only intent is to try to cut off avenues by which existing practice can be challenged.
It's pretty likely that mass surveillance is already in breach of Article 8 - the outrage at Snowden's revelations was mostly because of a fear that "national security" would not survive a challenge in the ECHR not because they threatened specific operations. The government and the security services knew that their activities were likely illegal, except under a very tenuous construction of the law, but were determined to carry on regardless.
There really is no intention to have an accountable system - the current draft bill simply makes it marginally more specific that the security services have much wider scope than has previously acknowledged, but makes it harder to challenge - or even discuss - them. If anyone comes close to challenging this legislation in future, more will follow and the goalposts will be changed as frequently as is necessary to scupper any effective action.