Very interesting take on how the two will show their unconditional love by supporting each other and be in each others mind and heart regardless of the circumstances but I wouldn't really call it 'platonic' because their scenes are already charged and when you say platonic it usually means no sexual desire at all. Definitely their relationship will be beyond any physical relationship which they will be deprived of but the burning desire to be with each other will always be there.
Thats the misconception about platonic...everything starts fron basics and physical attraction to a beautyful thing is a basic instinct of human,
Its not always the case as u said...physical love is quit biological...u do get physically attracted when u r different sex,thats how God has made humans or say animals ,its then when soul and higher conscious come in...many(human crowd) may get limited to physical pleasures while some (human radha krishn)grow up to higher levels and start inspiring there love for better and humanity...thats what platonic love and platonic relationship is all about in broader sense or say how Philosopher Plato describes it
Its not that platonic does not have sexual desires , its that they dont matter much when u r too busy with something much higher as humanity, spirituality ,patriotism, social responsibilities etc.
Saras and Kumud are two beautiful humans of different sex and physical attraction towars to beutyful selves is quit obvious and biological,it would be illogical and odd if they dont have it...but then its the start to something much more these two lovers will share in future then just mere sexual or pious love !!!