It would help if you limited it in scope to related areas. The scope of the current wording is beyond ridiculous.
As it stands the clause effectively prohibits anything done by someone employed by you, regardless of whether it has anything to do with the company or not.
Parts 15 and 16 are worded as IP and business protection. 14 is certainly over-reaching.
Taking the wording you have used it would appear that an employee has to request written permission from their boss to do practically anything:
* Participate in a code dojo or hackathon
* Assist a friend in moving
* Help someone change a flat tyre
* Change your own flat tyre
The absurdity of the examples follow directly from the absurdity of the restriction placed upon people accepting the contract.
Whilst an individual sensible enough to read the contract would likely raise issue with it, it is all too easy to pressure them into signing anyway with phrases such as "standard language", leaving all the rest not sensible enough trapped.
I also note it is ironic that you suggest an external lawyer gives free advice on rewording, presumably this lawyer would have to foresight to have pre-approved giving such advice with their boss as they operate under their standard contract?
Of course I understand this is very likely a complete oversight. And that GitLab is very unlikely to have any malicious intent in this. However I do find the existence of such a clause very alarming.