Unless you have another car and only need 1 car, I think it will cheaper for you in the long run to keep it as is. You've done a ton of maintenance so it should run trouble free for awhile. Modding, demodding and the modding will be more expensive...you will probably redo everything that you've done.
I drove my car with a newborn and moved my family from Columbia, SC to Leavenworth, KS to Killeen, TX in it. Not exactly an SUV but it works fine for a family. In fact, I think it is easier to get the kid in and out of the car seat in a coupe. More important when they get bigger and squirm a lot more. You slide your kid in from the front of the seat instead of hoisting him/her over the side.
The car is good on gas and is pretty safe too!
Only sucky thing is it eats tires. Just wait it out and stay the course if at all possible.
2013 F30 328i - Melbourne Red
2011 E90 M3 - Monte Carlo Blue
2004 E46 M3 - Imola red