4.3% hashrate is a good start
You have to actively switch to BIP148, so only a fraction of Slush hashrate counts toward BIP148.
I think the BIP148 movement is already almost dead, no business behind it, even most Core devs opose it. Compare it to SegWit2x, which seems very promising, business behind it and the discussion with Core devs is constructive so far.
I WOULD like to see an agreement to avoid UASF, the problem is, there's no way to do a proper hard fork in 6 months, I think 1 year would be better, oh and forget about anything that isn't Bitcoin Core approved. No one on their right mind is running software for a hard fork that isn't Core approved.
If we want to do this right, miners should follow the soft fork segwit activation then a hard fork later on, anything that isn't segwit via soft fork is a mess and a scam, since it doesnt end covert asicboost.