There is no problem with a blockchain size?

[nagamerah]

As we know each blockchain transaction has inputs and outputs
If all transaction inputs are spent then these inputs doest not contain important information anymore as it will not participate in any future transactions

And we can find blocks that consists of such transactions only and we can remove all this data preserving only block hash

So this means that a blockchain will not grow forever , it will grow forward but closer to the begining blocks can be replaced by its empty placeholders

Going this way we, of cause, lose transactions history but integrity would be ok