Look at the 10 minute block time restriction. Whatever you do with SegWit ( which is brilliant ), or with blocksize changes, you will still be looking at up to 30 minutes for a confirmation. That's a long time for an on-line service these days.
that would ruin alot of other outside economic and logistical aspects. by messing with difficulty and also the rewards.
think about it.. if long term investors see that blockstream hav messed around with the fundimental scarcity rule of the block rewards.. they will not trust that it wont be changed again later. thus losing any credibility that bitcoin is scarce.
let alone blockstream trying to be the defacto sole source of bitcoin changes, which is another issue that gets people annoyed about the promise of decentralized trustless code becoming not so decentralized because core want dominance
10 minutes is fine for larger purchases like a car or a house. LN wold solve the micro-instant online service demands