Hi there,
For example, the Input Locking Node can only be selected to lock an input, if its stake is no less than the input UTXO value.
If working like this then if I want to spend a small of money but I only have a very large unspent tnx output then my spending also need to wait to be locked by a big stake service node or have to wait long time to be confirmed by PoW, right?
Do you think that we can have another way to make the small spend tnx faster?
It depends on the input UTXO value, not output value. And it's for your own safety. People can send a small transaction from a large input UTXO, just to double spend another large transaction with the same UTXO.
Beside, you only have to worry about this, when you are some kind of top coin holder (like top 10 or something). With that amount of money, people usually wait for several confirmations anyway.