It is fortunate I happened to spot this question - I have dropped out of answering on AnswerBank - there's too much trivia and simply not enough decent questions (of this quality) any more to interest me.
The implication of this is that HMRC regard you as self-employed. Have you looked at this page of HMRC?
http://www.hmrc.gov.uk/sa/parts-partners.htm
The financial implication of that is that you have to pay Class 4 NI contributions on your income. This is because your employer will no longer be having to pay the 13.8% flat rate employer's NI contribution on your earnings. What uplift in your earnings does the LLP propose to make to your income to allow for this? - indeed has the LLP even acknowledged to you the impact of this change?
Now have a look at this page.
http://www.buzzacott....-or-self-employed/104
This particular article (from a firm of accountants) is arguing that HMRC may in future 'change the rules' about self-employed status of non-equity partners - because there is no risk v. reward element of capital injected by such people.
But read on further down - regarding the legal side the position is even more complicated as to whether (as a non-equity partner) you would continue to be covered by the main tenets of employment law legislation. I am aware of several legal cases (in this article quotes some) whereby an Employment Tribunal has decided that a partner in an LLP is covered for such aspects such as unfair dismissal claims. So I cannot say what aspects of employment rights you might lose.
What I would say is two things:
1) If an employer is determined to part with an employee, it will do so - especially in an organisation with predominently managerial / professional people - it boils down to how much money the organisation forks out to gain the agreement of the employee being released.
2) There has to be a level of trust in the organisation by the workforce - especially of the type you are in, that they will do the right thing by the staff. It doesn't sound like you have much trust in the motives of the senior partner(s).
If this was being done to me (and I have experience in working for a few professional services companies, which is what I suspect yours is), I would want considerable financial carrot to do it - not such a quid pro quo based on a change in NI contributions.
If you want to follow up with further questions, I will endeavour to respond, but this will be my last.