That's what I'm hinting at. I edited my previous post:
Monero has a hurdle in that Electrum style wallets come with a significant privacy cost. Will this be a scalability bottleneck?
I don't think so... and I do believe you and I have hashed this out before . Again, I think all thats necessary is a subset of the blockchain to provide adequate ring partners. So regardless of how large the whole blockchain is, you can maintain simply 2 gigs of random blockchain data and your wallet can select from those outputs. This 2 gig subset will refresh and change on some schedule.
Trust me, if I knew how to code this is what I would figure out.
Well, that and remote transaction pushing. Stupid work eating my time.