Tumbleweed
I can see building destruction and repair being usable during events, but in OP battles? What's the point in that? Attackers would gain no benefits from that, and defenders probably wouldn't bother much, as drills are relatively cheap and can be thrown out with no regrets. As long as there is no griefing guild that would make fun of destroying others drills, this feature is useless for battles.
which is exactly what it'd be used for, people vandalising outposts outside of op battles out of spite or whatever...
In battles, a losing attacker would likely do the same, cause damage to the outpost out of spite.
It would add an element of depth to gameplay if outpost buildings without regular active maintenance by the owning guild would deteriorate over time, maintenance consisting of guild missions to do repairwork, repel bandit tribes and incursions by kitins and other wildlife, etc. without the possibility of assistence by other guilds (so as to prevent alt guilds from holding outposts, see also next point).
If no such missions are successfully completed over time (and the number needed could go up more than linearly with the number of outposts, say 1 mission a week for 1 outpost, 1 mission a day for 2 outposts, 1 mission an hour for 3, etc., thus making it harder for guilds to hold multiple outposts) the outpost would fall fallow and any guild can claim (after missions to rebuild it) ownership, except the guild that was lax in their duties.
Mission difficulty of course dependent on the outpost level.
No more inactive guilds with outposts, no more guilds holding 5+ outposts with 2-3 people and a strong guild backing them from the outside with threats to attack anyone who dares oppose them.