There is an amount below which an IVA becomes no longer viable. This is usually around the £90 mark, though I have seen a few a couple of quid under that. If this intended move is voluntary, rather than something forced upon you, I can see creditors taking a dim view of the reduction. Yes, a creditors meeting would need to be called for such a reduction and, of course, the more compelling reasons you can come up with, the better.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk