All considered, I wouldn't mind either reduction or original scale.
Depending on the vibes they'll be giving me, I'll convert them into heavy infantry or full powered super marines.
With sci-fi we're given different rationales for scale difference.
Low gravity worlds would account for tall, gangly people, while genetics and prosthetics would create huge hunks of power-armored soldiers.
Sure, weapon scale can be a problem, when converting.
But actual firearms come in all sizes, and re-sizes, accounting for different calibers, more compact designs and different alloys/polymers.
My only concern is picking the right base size: 25mm for "normal" people; 32mm for very large, tall, bulky or fat people.
Sure, wrecks havok on pre-gridded maps, but tall minis on small bases irk me more.