Of course it's not naive - we all want what's best and in an ideal world we would supply our Armed Forces with nothing but the best equipment in adequate quantities for all the roles they are required to fulfill - but there is no money for this so we're fudging along with a plan that makes very little financial or military sense. With that in mind and considering the treasury has committed to buying the CH47 anyway, then surely that is a better and cheaper option than refitting an aircraft that does not require it and losing a wealth of experience in operating Merlin and the expense of retraining those that are lucky enough to escape the inevitable redundancies.
Of course, in an even-more-ideal world, the Navy would sail all of the ships and boats, the Army would drive all of the vehicles and fight on the ground, while the Air Force would do all the flying. If our services were that clearly defined, there could be no inter-service bickering over who should be flying what or land-grabs for equipment from their warfighting brethren.