I find the engineer has some pretty useless downed skills, compared to some other classes. In particular the lack of a ‘escape’ skill is rather painful. We have no way to escape from a dangerous area, be it siege fire, enemy zerg, or other. Other classes can vanish and change position, turn in to mist and move away to safety, but all we have is stationary, we never move, and are sitting ducks.
And so I propose to replace the third skill, the explosion, with a Rocket Jump. You activate it, and get a target selection circle, you pick a spot and desperately fire off your rocket boots, flying to that spot. The jump might initiate a small knockback to the surrounding enemies – bu that part doesn’t matter, most important is the ability to move away when downed, so people can revive you – for example if you got downed at the keep doors while repairing or attacking.