I have to say I agree with Buffy. Easier just to accept in the end that you have to please the people with the power. Particularly if your supervisor, and your whole thesis committee/examers agree. More than that - adding stuff you think is unneccesary to appease some outside assessor is the daily bread and butter of academia, where reviewers are always asking for things the author thinks is unreasonable.
I'm still not sure what system you are working in, but the way you talk about viva's and thesis corrections makes me think you are in the UK or a similar system. Note that while in the US, I don't think corrections following the defense are common, in the UK almost all candidates are asked to make correction before being awarded the degree.
Corrections at my university come in three flavours. You can read the details here:
Your univeresity should have something similar.
The extracts for minor/major/rewrite are below. Note in all cases the phrase "to the satisfaction of the examiner(s)". The examiner decides how relevant the corrections are. The examienrs decide if you have done enough. There is no negotiation. Usually one of them is nominated to make the decision. Usually the internal for minor or simple major corrections, both the internal and external examiners for more substantial corrections. Once you are at this point, you more or less have to do what the examienrs say if you want your degree. You might have a case if the corrections required of you are outside the bounds of the grade (i.e. if they asked for new reserach, but called it major, rather than rewrite), and there is an appeals process. But I have never heard of a university over turning the judgement of an examiner.
That the degree be awarded once specified minor corrections have been completed to the satisfaction of the examiner(s)
This option may be chosen where the examiners are satisfied that the thesis meets the requirements for the award of the degree, but where there are minor weaknesses or editorial errors that must be rectified before they can recommend the award of the degree. The nature and extent of the required corrections must be genuinely minor in nature such that they can reasonably be completed within a period of three calendar months from the date the candidate receives notification of the required corrections from the examiners.
The candidate will be expected to make the corrections without undertaking any further original research. The examiners are responsible for providing the candidate with the details of the required corrections and must stipulate which of the examiners will be responsible for approving the corrections prior to formal recommendation of the degree.
That the degree be awarded once specified major corrections have been completed to the satisfaction of the examiner(s)
This option may be chosen where the examiners are satisfied that the thesis has the potential to merit the award of the degree for which it has been submitted, but does not yet satisfy the requirements for award and contains deficiencies that are in excess of editorial or presentational corrections. This may involve re-writing sections, correcting calculations or clarifying arguments, but should not require the candidate to undertake any further original research. The candidate will be granted 6 months to complete the required corrections from the date the candidate receives notification of the required corrections from the examiners.
The examiners are responsible for providing the candidate with the details of the required corrections and must stipulate which of the examiners will be responsible for approving the corrections prior to formal recommendation of the degree.
That the degree be not now awarded, but that the candidate be allowed to submit a revised thesis after such modification of form or content as the examiners may prescribe, WITH/WITHOUT oral re-examination
This option may be chosen where the examiners do not feel able to make a recommendation for the award of the degree at this time. The thesis requires substantial corrections in order to meet the requirements for the degree, but the examiners feel that the candidate is capable of revising the thesis, to their satisfaction, within one year.
The candidate is required to formally submit a revised thesis within one year and the examiners must indicate whether the candidate must undergo a further oral examination. Examiners are asked to consider whether an oral re-examination would help the candidate to justify the additions or alterations that are to be made to the thesis. Where the examiners’ original recommendation specifies that a further oral examination is required, this should take place, regardless of the outcome of the examiners’ preliminary assessment of the resubmitted thesis. The examiners should provide the candidate with full written details of the required revisions to the thesis, normally within two weeks of the oral examination. The same examiners will normally re-examine the candidate.