It's being tested on the Elements Alpha sidechain for over 12 months, segnet for 6 months and now on testnet3 for the last 7 weeks ... so what kind of altcoin did you have in mind specifically that would be needed in addition to these?
Preferably one containing and transferring enough value to be worth attacking.
MAJOR CONTRADICTION ALERT
If that's true, how is that people like you have used nothing but words to attack Segwit, then? You could've used the coding geniuses behind your preferred route for Bitcoin development to demonstrate how fragile Segwit is on the network.
Why, with months of opportunity, hasn't the public testing of Segwit been successfully attacked or exploited by
any interested party? (let alone those Core detractors who claim they have coding talent)