Curly.
Unless you want to micromanage your SDMP then let the maintenance company do the hard work. You are finally responsible for your program (according to the new law) but in essence this doesn't mean you have to sit down and design a program from scratch. You will not be signing the aircraft as serviceable, just signing for how you decided it should be regarded as serviceable. The responsibility for carrying out the work and conducting the ARC is still the domain of the engineers so be guided by them.
Having had a quick look through the available guidance EASA did mention that any program should be pre approved by your NAA, however the CAA's guidance (and declaration form) makes no mention of this. After all, you make the declaration of what your program is. The person doing your ARC and the CAA have the right to say it's not good enough.