This is something, as someone pointed out, that can be easily done in an ethereum-like platform.

In bitcoin, you might need a new opcode that restrains the spendability of an output in the following way: it is spendable only togheter with other outputs that refer to the same address and so that the total amount to be spent is equal or greater than the required sum... or something like that.

I think this is an interesting use case, so maybe it could be worth a new opcode.

best regards,
ilpirata79