Since BIP148 is a soft fork, once it gathers sufficient hashpower the entire network will converge on it as the longest valid chain
In a non-controversial softfork, where e.g. 10% of miners “forget” to upgrade, you’ll end up with 1 in 10 blocks getting orphaned at random. Non-upgraded miners will follow each reorg, dillegently applying their hash power despite having lost a block.
As a regular bitcoin user, whether your node supports the soft-fork or not, you’ll never be on the wrong chain for more than a few blocks. Conventional wisdom seems to be that 6 confirmations is plenty.
BIP148 is controversial which will lead to a non-random pattern. If more than>50% of the miners decide to resist it — e.g. because they don’t believe it has economic majority support — the chains may diverge for many blocks. How many? A dispute could drag on for weeks if not months, especially if it leads to a war of attrition.
This puts regular bitcoin users in a very serious predicament. They need to decide immedidately which chain to follow, and stand to lose a lot of money if they make the wrong choice. The conventional wisdom of 6 confirmations no longer holds. That needs to be communicated to every single bitcoin user on the planet, and I’ve not seen any credible plans to do that. Even if it can be communicated, not all commerce can afford waiting that long.
I think that in order to avoid “logistical nightmares” you need either overwhelming miner support or overwhelming economic majority support.