Owning a 14 plate FR Tech pack, I've done few changes, well worth. Some of them are sorted in newer version, but may give you some ideas.
First was installing the fan washers. Cheap and efficient. Dead easy to do.
After that was more about my personal choice, better sound proofing, but it's not for everyone liking to take the car in pieces. Used 2mm Silent Coat inside the doors, under rear passenger seats and the whole rear wheel arches and boot. Well worth if noise upset you.
Next step was the auto wipers/auto lights that for some reason wasn't installed in my car. Basic stuff. Installed together with auto dim rear mirror.
Replaced rear indicators, front fogs, rear fog and reverse lights with LEDs as all the interior lights.
From all the changes, the more complicated one is removing/re setting the door panels, as it must be perfect to avoid any noises and rattles.
Fisically, that's all the changes. Planning to install the sub and central speaker, but not any time soon.
Using OBDEleven a lot of changes, well worth.