Custom auto exhaust shops have the skill, machinery, need, and experience to do this and harder stuff every day.
CAVEAT... usually in 3" or LESS. But, even so, large trucks exist, too, so it is "plain old white bread" in their world.
Same-again folks who make sectional tubing into tent-poles, weed-wacker shafts, outdoor lamp posts, and assemble-it yerself furniture ...but not-only.
IOW swaging is "an industry" and not a minor one. Saying "impossible" just doesn't seem to fit? At all.
@ a mere 100 units, I'd go and find a specialist with the powered hydraulics, mandrels collection, and experienced skills already to-hand.
I would NOT tool-up for it unless you knew it was but the first order of many.
Even then... a specialst partner or few makes more sense to my bean counter side than diverting from your main line of work to f**k-around in some OTHER expert's wheel-house is likely to make! Generally faster, saner, lower risk, to do what you do best, trust other's to do the same?
2CW