First of all, the 100/25 or 6 months and an upgrade test (a choice.) is a sensible answer the the problem.
To answer GusHoneybun, this is a situation where the employer should cover the cost. The person concerned has been paid a reduced salary until then, will now be a better asset to the organisation and of course the employers' cost is not as high as the normal rates for the aircraft...and it's tax-deductable.
To respond to the comments of Whopity, I'm not sure that the requirement for 200hrs. was fact. It certainly wasn't in the late 60s I feel certain.
Besides, the number of hours of instruction to reach the magic "25" will probably be in the region of 375 anyway (unless you're poaching or there's a fiddle going on.)
Actually the points made regarding attitude, communication and pure teaching skills are far more relevant to the arguement than "so many hours" as is the case in so many aspects of aircraft operation.
"Hours," per se, will never be the right answer. That's why an upgrade test, by someone qualified to judge, should always be the preferred option.
Rgds, Sleeve.