I'm sure they'll manage to Club Class a few admin types around the World to set the capped rates and check up on crews when they are away...
How about a flat rate of £40/50 per 24 hrs,wherever you go, on base,off base, doesn't matter, you gain on some stops and lose on others. "Lean" all of the jobs in handbrake house that spend hours collating
every imprest and save some money that way. As far as accountability goes we'd probably have to employ some form of trust
and do random percentage checks of the imprests to satisfy the treasury. End result...Aircrew happy, far less niff naff and trivia to keep the admin world busy