OA whilst I applaud your determination to succeed I am also worried that you haven't really thought this through properly. Lower limb lengthening alone will not solve your problem because, as you know, people with Achondroplasia also have short arms which would probably prove to be a real problem for you as you will need to be able to reach all switches, and have full and free use of the controls. I also feel that you have a slightly unrealistic view of the timescale for your operations and recovery and possibly also of what can be achieved for you. Just because a few people have been able to achieve a 14" gain in height does not mean that everyone who has the operation will do so and it may well take more than the twelve months you have allocated yourself, also, the older you get the slower your rate of healing. You may not achieve the height you hope for but may well be able to fly light aircraft so do think about other careers in aviation eg good Flight Instructors are worth their weight in gold and are essential to the industry - after all, if they didn't exist there would be no pilots.
Good luck, please let us know how you get on.