Trimble and Nagusa scored three tries between them in last weekend's bonus point win over the Scarlets.
McLaughlin's 25-man panel also includes back rower Chris Henry who was ruled out for the Scarlets game, but lock Dan Tuohy remains on the injury list, along with full-back Bryn Cunningham and scrum half Cillian Willis.
Centre Paddy Wallace, Ulster's acting captain, told IrishRugby.ie: "Our focus is on Bath at the moment, we have Edinburgh the following week. We won't look too far ahead - we want to take care of Bath on Friday.
"Bath are coming off a turbulent off-season. They've had a few problems in the club, obviously they lost four key players.
"But at the same time, I think that's binding them together into a very tight unit. I've no doubt they'll be focused on trying to beat us and getting their Heineken Cup campaign off to a good start in Belfast.
"We can't take any complacency from the last two games into this match, and we have to come out all guns firing and sew that seed of doubt that Bath may have, having not started the season as well as they would have liked to.
"Regardless of league form, Bath are very capable of delivering performances on the day and certainly beating any team. As I've said, there'll be no complacency from our end, going into the match."
He added: "We're in good shape. The brand of rugby we're playing is much improved and much more entertaining for the fans.
"That's spread from the confidence of the coaches that they have in the players. Brian is willing to pick young guys and through them in and give them their rewards if they play well, because he's not scared of dropping more of the senior players as well.
"That confidence that Brian and the rest of the coaching team put in the players is really shining through."
The 23-man matchday squad will be announced on Thursday afternoon, including an extra prop replacement as per the new ruling.
ULSTER Squad (v Bath) - Backs (11): Isaac Boss, Paul Marshall, Ian Humphreys, Mark McCrea , Paddy Wallace, Darren Cave, Ian Whitten, Andrew Trimble, Timoci Nagusa, Simon Danielli, Clinton Schifcofske.
Forwards (14): Tom Court, Bryan Young, BJ Botha, Declan Fitzpatrick, Andy Kyriacou, Nigel Brady, Ryan Caldwell, Neil McComb, Ed O'Donoghue, Thomas Anderson, Stephen Ferris, Chris Henry, Robbie Diack, Willie Faloon.