If the "Old Bridge" on US 190 is upgraded, they could do something like they did with the Huey P. Long in NOLA and simply strengthen the existing trusses and widen the existing roadways to 3 lanes with proper shoulders. They could also simply build a separate single span for the highway portion and either tear down the existing highway portion or convert it for pedestrian and bike usage, or just tear it down completely.
There arises an issue, however, with the eastern approach: there's an underpass where the Baton Rouge Southern (ex KCS) rail line crosses over the US 190 mainline, and then there is an at-grade crossing of the CN (ex-IC) rail line where there's also an intersection with an access road to the aluminum plant. Monte Sano Avenue, which parallels US 190, also crosses the CN line there as well. How they are going to get a freeway/tollway through that towards the Scenic Highway interchange (a scrunched cloverleaf) is going to be interesting.
If one could take a time machine back 60-70 years, one wonders how Louisiana/Baton Rouge would have dealt with that if the original I-410 would have been built.
Yeah, about that original I-410 proposal....wasn't that to use what is now I-110 through downtown to Airline Highway, then double back using the US 190 bridge and then LA 1 or a new corridor just west of there?
Also....I thought that 410 was also the number that was proposed for the Dixie Highway bypass of greater New Orleans? (Of which I-310 and I-510 were its offshoots.)
Something like that...
(Thought I had a better scan of the Baton Rouge inset, in the lower right corner)

la_rand_62
Found more info on the proposed original I-410 in BTR.
Apparently, it would have used what is now I-110 from its current downtown terminus to Airline Highway (US 61-190 Bypass), then turned west on an upgraded US 190 using the existing "Old" Mississippi River bridge to just west of LA 415, then turned back to the south to reconnect with I-10 west of Lobdell.
Basically, it would follow the western portion of what is now proposed as the Northern BTR Loop, but then double back down existing I-110 rather than continuing down Airline Hwy to Plank Road, then cutting northward and eastward north of Denham Springs and Walker as the North Loop is proposed to do.
When that was cancelled, they then decided to extend I-110 northward through Scotlandville to its current terminus in North BTR at Scenic Highway (US 61) near Mills Avenue, just north of the Southern University campus.
Source page for this (and also the proposed I-410 Dixie Highway in NOLA):
https://www.interstate-guide.com/i-410-la/