IMHO aimbotting is not as much of a problem in Trem as it might be in other FPS games.
First of all, Trem has spectator mode, which can quickly reveal the actual aimbotting.
Second, there's more to FPS then perfect aim, and a lot more to Trem then to the average FPS. Even assuming that a hacked client can detect being specced and turning off aimbot, you can still recognize a bad player. Heck, you don't even need spec for that (although it definitely makes things easier).
A decent Trem player is more than just a person who roams the map shooting their gun or pointing their alien perfectly, in between trips to the armory for restock. You need to know
when to shoot. You need to know how to dodge (you can instantly recognize a skilled dancer.) You need to know when to attack and when to retreat. You need to know how to fight alone as opposed as fighting as a group. You need to know the maps and make use of strategic points in both hand to hand combat and building or attacking. You need to use your alien or weapon+armor properly. You need to choose what alien or weapon/armor to use in particular situations. You need to work with the team and communicate. You need to recognize how the game turns and adapt your tactics.
I could go on but I think you got the point.

All these things usually develop together in an honest Trem player. So if you see a player who is a perfect shot but can't even move efficiently and disregards all the finer points of Trem you can suspect aimbotting even without actual speccing.
Third, there are things particular to Trem that make aimbots a thing of limited use. They are not effective for slow-firing weapons and using aimbotting for the pulse-rifle or luci has got to be downright dumb. As is using an aimbot for anything bigger than a mara -- if you need to that you need glasses not an aimbot. And of course, since it's a team game, one player using an aimbot does absolutely nothing for the team in the long term, if the other team is half decent.