There's already one PvE mission but you have to play it solo. Why not expand it to a four player team? Add in a boss robot and maybe even multiple objectives instead of just one? My biggest lament about Overwatch is it has some of the most fun co-op missions I've ever played in a PvP game but you can only play them for one month out of the year. If Ironsight had similar types modes but up all year long that would go a long way. Personally, I think any of the maps already in use could easily accommodate fun assault/horde type PvE missions as they are. Just throw a bunch of sentinels at us, maybe some A.I. controlled human characters and let the chaos reign!
These pve is easy as hell. Second - this is so boring... Where is defense mod