The changes could be seen as enforced - given Mike Fitzgerald was suspended and Liam Squire failed a concussion test - but the Chiefs are confident the new faces will help solve an old issue.
"The Brumbies have got an outstanding set piece, it's very destructive, so to have Mo and his experience is a hell of a bonus," Rennie told Radio Sport. "He's obviously a strong scrummager and a good lineout thrower, so that will give our team a lot of confidence in those areas."
Rennie thinks that will ring especially true if the Brumbies opt to scrum for penalties and drive the lineout for the same result.
Against the Crusaders, the Chiefs' hesitancy was such that they often eschewed the full lineout in favour of rushing an abbreviated option, leading to a lack of composure at vital times.
The Chiefs must be able to depend on their lineout if they have any desire of controlling the ball and giving their unusually subdued attack - with two tries in the the last two games - a chance to break free from the shackles.
Clean ball might be a luxury against the second-placed Brumbies, though, and forwards coach Tom Coventry would settle for his charges merely emerging from the set piece with the pill in hand.
"The key to any good lineout is variation," he said. "Ideally, the ball coming off the back of the lineout would be the best. But I suppose our philosophy at the moment is you get it won and you have the ball tucked under your arm for a little bit.
"We play pretty good footy when we've got the ball, it's just a matter of keeping it."
To aid in that simple strategy will be the presence of Crosswell and, for the first time this season, Filipo. With the combined knowledge accrued from the pair's years on the paddock, Coventry thought the Chiefs would be better equipped to deal the pressure situations in which they have faltered.
"Crossy's come in and Ross has a ton of experience, not only at running lineouts but he's pretty nimble in the air as well. We've got two good lineout forwards back into the mix and hopefully that stability comes with that experience."