*CAVEAT: Nothing is going to replace Giannis. He's one of the best players of all-time. But if he's going somewhere, this might be the play. Lifelong Pacers fan, I'm making this trade even if we win the Finals.*
The more I think about it, I think ++the Pacers might be the best landing spot++ for Giannis while offering the best compensation for him in return. The worry the Bucks have is that they don't have their own first-rounders until 2031 so "they can't tank." They prefer to remain a playoff level team without Giannis, at least for a couple of years, and this does that.
I love Pascal Siakam, I always have. He's honestly the best comp in the league for Giannis... but Giannis is a huge upgrade. He lacks the reliable shooting efficiency but he does everything else at a much higher level and higher volume. If the Bucks had a coach, Giannis would already be scoring 6-8 points per game on leak outs like Pascal does. (If only the Bucks had a coach.) The combination of Giannis + Tyrese would be devastating (unlike Dame, Tyrese can actually pass in the PNR). Myles Turner is a younger better Brook Lopez, and the Pacers still have all of that swarming offense/defense depth.
Siakam is an All Star caliber player already and in a straight up replacement he is going to give you 24-8-6 on good efficiency plus 3-point shooting and reliable free throw shooting at PF. (He would flirt with All NBA.) If you squint, the do-it-all, rangy, utility knife forward who can defend 5 positions and score effortlessly on the fast break wearing "43" is going to remind you of "34" even if he doesn't totally fill the void.
Mathurin is still just 22 years old (players will be drafted this season who are older than Bennedict Mathurin) and has high upside. He's a massive upgrade on Kyle Kuzma at SF and would be their best SG as well. It wouldn't be surprising at all for him to become a +20ppg scorer on decent efficiency and higher volume.
The picks are also valuable: 4 first rounders, along with 3 second round picks that are likely to come high in the draft order. Giannis will push those Pacers picks down, but maybe not, maybe the Bucks trade a falling star and this is a huge windfall for them.
There is also the secondary market as well: If the Bucks end up not winning with Siakam-Mathurin (or simply not wanting them) they could pivot again to trading them for more assets. Both Siakam and Mathurin could draw multiple first round picks, potentially brining the haul to +8 first rounders over the next six years.
Fanspo has the Bucks losing 2 games here and the Pacers +8, which I think makes the case for both. This moves the Pacers into the perennial 60-win range and also bizarrely puts two of the sport's most marketable stars in Indianapolis! (Caitlin Clark and Giannis are going to sell a lot of merch.) Meanwhile, the Bucks remain a playoff team – this is a 4-5 seed indefinitely as you wait for 2031 to fully reset. And an odd benefit for fans, they'd still see a lot of Giannis.