Rumours persist that long-time Scarlets coach Jenkins could also return to the region as Elite Performance Director.
The Llanelli-based region lost the reverse fixture at Parc y Scarlets on Boxing Day 14-21.
Eifion Roberts (Sale), Dan Biggar (Ospreys), Martin Roberts (Scarlets), Powell and Halfpenny were called up.
The Scarlets mounted a fightback in the second half but Bristol defended well against relentless pressure.
However, despite poor discipline and handling errors, the Scarlets came back into the contest.
"I did a lot of work with John Muggleton down at the Scarlets, " said 23-year-old Priestland.
BBC: Rhys Priestland hails John Muggleton's role in his rise
His colourful career took him to Swansea, the Ospreys, Bristol, Harlequins, the Scarlets and Pau.
The last time Scarlets were successful in Europe, they beat Munster in the 2006-2007 quarter-finals.
"It's so important to us as a region, " said Scarlets team manager Garan Evans.
The Scarlets become the 24th and final side to make next season's Heineken Cup.
James followed flanker Gavin Thomas and New Zealand lock Simon Maling out of Parc y Scarlets.
He will also miss the big festive Welsh derbies against the Scarlets and Cardiff Blues.
They plan a player development pathway between the Scarlets academy and the university's School of Sport.
Scarlets prop Huw Gustafson broke his leg in their Regional Under-20 Championship match against the Blues.
BBC: Sowden-Taylor grimaces as his ankle is caught beneath him
But the Blues held on to also send the Scarlets into next year's Heineken Cup.
Clermont Auvergne's bonus-point victory over the Scarlets relegated Wasps to third place in the group.
Stephen Jones kicked Scarlets ahead before going off with a shoulder injury that will worry Wales.
Injuries have severely disrupted the Scarlets captain's career since his Wales debut against England in 2001.
The Blues, Scarlets, Ospreys and Dragons then turned down the WRU's player-release compromise of eight days.
The Wasps boss said they face some "tasty" pool games against Munster, Llanelli Scarlets and Clermont.
"The Scarlets have approached us but no substantive detailed conversations have taken place, " Lewis told Scrum V.
However, the Scarlets had the consolation of Sean Lamont's late try from a perfectly-weighted Stephen Jones cross-kick.
Morgan Stoddart, Jones' Scarlets team-mate, has been called into Wales' autumn Test squad to replace 29-year-old Jones.
Llanelli's new 15, 000-seater Parc Y Scarlets home opened last year as Stradey Park made way for housing.
He also accepts the Scarlets' efforts to develop rugby in north Wales have not been entirely fruitful.
BBC: Scarlets coach Nigel Davies wants Welsh regions rethink
Scarlets full-back Morgan Stoddart and Dragons scrum-half Andy Williams are also fresh faces since the Six Nations.
With half-time looming Tom Riley made the best break of the half, splitting the Scarlets' midfield defence.
But the Scarlets crossed for two tries in as many minutes to set up a nail-biting finish.
Scarlets scored a try first through Regan King, but David Wallace romped over before half-time for Munster.
Ulster should have been further ahead at half-time but their indiscipline kept the Scarlets in the game.
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