We have a somewhat screwed-up AD domain structure. At some point in the past, Domain A was the parent to Domain B. We have two locations, so I believe previous IT staff set up the remote location as a child of our existing domain. At some point before I worked here, there was a serious problem with network and whatever consultant was brought in to fix things wound up changing things around so that Domain B is now the parent of Domain A. I really don't know more detail than that, but this is what I've been told.
At a later point, but also before I worked here, the IT admin at the time created a new domain in a new forest, thinking that we needed to start fresh. The problem was that there were, in his words, screwed-up permissions due to the parent/child switcheroo. (A big part of our problem is that, although we do pretty well managing the network, neither he nor I is an AD expert.)
A big piece of this migration, which has been going on for quite a while now, is moving Exchange into the new domain. This would involve cross-forest migration of all mailboxes (~180 users), and is not for the faint of heart, from what I understand. Particularly since downtime is absolutely not an option.
A consultant that we hired to help with the Exchange migration got seemingly nowhere after 6 months, so we found someone else, who seems a lot more qualified. This new consultant says that, although we can migrate to a new forest, it's a much bigger deal, more expensive, and will take more time. His suggestion is to do a domain rename instead.
As we evaluate our options, I'm looking for advice from other experts out there. Does what this new guy says sound reasonable? Is it wiser for us to consider a (supposedly less expensive and easier) domain renaming process of our two current "old" domains rather than migrating everything to our new domain in a forest? Thanks in advance.