Just give it two "shots", first one fires the bomb which starts x numbers of seconds until self-detonation. The second "shot" detonates the explosive remotely, lesmok makes it an impact detonation bomb (no second shot) as would lochnagar while heatsink gives you two bombs before you can detonate both with your third "shot".
Damage type is harder, explosive and shatter probably make the most sense. I'd personally have a large amount of explosive followed by a large AOE low-moderate shatter damage (lumberjack sized area). give it a painful 20 second reload and harpoon firing qualities.
I wouldn't have it push people, if a heavy flak doesn't push you a sticky bomb probably shouldn't either.
Terrain sticking eh, but ally sticky hell yeah. Friendly fire (damage) probably not because trolls but being a mobula with 5 of these, sticking all of them to your pyramidion and having him ram the enemy while your crew just hits a button would be awesome (although more awesome if friendly fire was a thing xD). They could also have defensive value that mines somehow lack, fire one onto your ally and watch the noob try to ram him and get a face full of love.
I'm assuming the enemy wouldn't know that they'd been hit either (no base damage when it attaches) so a sneaky squid could shoot the rear of your spire and detonate the bombs just as the squid's ally closes in and you have to hightail it out of there, giving it even more of a cooperative style.
But yes I vote for heatsink mobula with all 5 sticky launchers shooting 10 onto his ally who then screams "OH WHAT A DAY, WHAT A LOVELY DAY" and sends himself to Valhalla while attaining the game winning kill with a ram.