There is no "reserved for future use". Franky is a misleading statement incarnate.
The Segwit testnet mined a 4MB block, just by including alot of multi-signature transactions (which obviously have a much heavier transaction:signature ratio than regular transactions)
So is this the extreme case where a large number of inputs is used in a transaction to fill up the segwit space?
The opposite
Multi signature means a single input signed by more than one key.
How can you pretend not to understnad something so simple.....