Most of it would be pretty tricky/expensive...
Heated Seats: You'd be replacing the whole seat, and there's also a button for it on the dash, therefore tricky and expensive. You could also just do s simple after-market heating cushion, though.
Radio Interface / Steering wheel audio controls: There's been threads on this already, but it essentially requires a whole new steering wheel, and likely a new radio unit as well. Likely a fair bit of wiring as well, unless it's all just plug and play with the right wheel and stereo.
After-market remote starters: There's tons and tons of after-market options of remote starters, typically ranging from $99 installed to $500.
Sounds like you maybe shouldn't have picked up the base model...?