There are a few races with a bonus to grapple. There's an augmentation that gives +2 grapple, but it doesn't stack with a grapple weapon bonus.
Currently, grapple can be a roll against normal KAC, and I would not expect better than that to become possible, since Starfinder has been making a large point of preventing excessive bonus stacking.
I do not know of a way to get to better than KAC+2 as a target for disarm, but you can still use anything that would help attack rolls, like a flat-footed target, or a wisp ally spell providing a harrying fire bonus.
In terms of improvements that are not a straight bonus to the roll, there are garrotte weapons, to deal damage on a grapple attempt, and there is the operative exploit Disarming Shot, as an alternative to a disarm roll, though it does require ally coordination, as you would have no action left to grab the dropped weapon, yourself.
Bull Rush has the most bonuses, you can get it very likely to succeed, plus a damage rider from the Armor Storm soldier style.
I recently made a Barathu mechanic who always rode his drone during combat to play the Against the Aeon Throne adventure path. Conceptually he had a gladiator/street fighter theme for his background. I gave his drone improved combat maneuver grapple. They would charge into the thick of combat and the drone would attempt to grapple their opponent and the rider would then stab it with his tactical spear.
It was fun to play, but my success rate in grappling wasn't particularly high. Though after getting in close I could make three melee attacks between the drone and rider. The drone only needs one so called appendage to grapple so I gave it two melee weapon arms one with a battle glove cestus and the other with an assault hammer.
When I hit with multiple attacks I did some impressive damage especially when I used the Barathu's special ability to double its strength bonus damage. However, since I was a mechanic I didn't hit as often as I liked, I didn't have a lot of stamina and hit points, and I sacrificed intelligence points to up strength so I only had 2 resolve points. On top of that the biggest problem was because I was right in the middle of the fight all the time everyone attacked me and even with heavy armor I was taking so much damage every combat.
I'm currently playing a grappling focused Skittermander in a Dead Suns campaign and its quite fantastic. As Hammerjack points out, you can get to KAC+0 equivalent (Improved Maneuver feat, a racial +2 bonus to grapple, and then either a grapple weapon or the grapple augmentation), which puts you at a very reasonable chance to land a grapple each round. Plus, due to the grappling rules being simple and straightforward, you have a decent chance of getting a pin in round 1 as well!
The grapple and pin debuffs stack well with what other classes are doing, and pin ends fights quite handily. Plus, grapple weapons give you a small amount of damage on a successful grapple attempt as well.
I'd recommend giving it a try!