After a lot of reasearch on the net, I still can figure out if the following idea is relevant or not :
I know (or at least I think I know) that each transaction consume all the bitcoins present at the inputs addresses. So if a bitcoin address is in the inputs of a transaction, you don't have to look at all the transactions older than this one to know how much bitcoins there is for this address. That means that we could remove all these olders transactions from the blocks keeping only there hashes via the Merkle pruning trick. With time, the Merkle Trees in each old blocks will become smaller and smaller so that space can be spared.
I understand that it will erase forever a part of the transactions, but the number of bitcoins for each bitcoin address will remain correct and perhaps that's the price to pay to keep a managable blockchain.
Is there already some work in this direction ? Is this a stupid idea ?
Thank you for your help