I dont think that's possible, if you remove the sims it stores all your stuff :( Best thing is to sell everything I guess. Not to mention, if you start over you'll lose a lot of ingredients and be a sims hobo with very little money. Because most players have A LOT of simoleons so everything is way to expensive for new simsies. I found that out when I played sims on a friends account who has to save up heaps just to buy a new hairstyle.
So just sell everything and start with an empty storage - not sure what your reasons for starting over are but thats the only advice I can give. You can change everything about your sim as well - though for gender change you need simcash I think :/
I haven't been playing long. I had A computer but I had to let it go back. I was paying on it but I couldn't pay anymore. I tried to play on my smart phone but for some reason it won't load the game past 80% so I can't play anymore. I thought it would be better if I just started over when I Could get another computer.
Thanks for the advice.