in the past, hilton has been pretty agreeable to comping silver or gold status (much to the consternation of existing elite hhonors members), but that may be changing now that there are more stringent qualification requirements.

in any case, i doubt very much that they would comp diamond status.

several years ago, the marriott in century city (los angeles) changed over to a park hyatt and hyatt comped me in as a platinum (or whatever level it is that's comparable to marriott gold) without even asking. no documentation was required, as they already had the records in their computer system.

your best bet may be to deal directly with the management of the property where you'll be staying the most, rather than the hotel's corporate frequent guest office. they may be able to make it happen for you if they're convinced your repeat business is worth the efffort.

it never hurts to ask ...let us know what they tell you.