Scrapper - Flamethrower Scrapper Roamer - MetaBattle

General

投掷H型试剂 counts as a healing skill and therefore applies superspeed. Another elixir toolbelt with a similar effect is 投掷U型试剂. These are great at both sticking to targets and escaping from them.
空投补给 is both a defensive and offensive elite. The CC and extra damage is good in any situation.

Damage

Most of the damage on the build comes from spamming 烈焰喷射 on Flamethrower.
- 重金属 and 质量动能 passively stack 威能 and 稳固 while in 喷火器 kit.
You passively stack 威能 while under the effect of 稳固. Space out 投掷B型试剂, U型试剂 and the passive Stability from Juggernaut to have as close to 100% uptime as possible.
超级迅敏法印 applies Quickness on a 20s ICD, which lines up with the CD of 雷霆一击 perfectly.
烟花古物 activates on 雷霆一击 and 功能机型.
Hammer is still useful for delivering burst damage especially after a CC, and might be a necessary finishing move for you after you've pushed a target to low HP.

Sustain

Swapping in and out of 喷火器 every ~9 seconds in order to to proc 洁净法印 is the closest thing you've got to a mass cleanse.
Other than that, you'll need to rely on elixirs for cleansing - every elixir removes 1 condition, including toolbelt skills!
Hammer mostly fills a defensive role, although it has good damage. Use it to block, evade and reflect attacks if you're starting to take too much damage in melee.
Flamethrower's toolbelt can insantly apply to nearby enemies while breaking stuns.