Like most, I usually shoot for weapon types and unit types first. That being said, when I play US Ariadna, everything can be anything. Grunts, marauders, Ohios, they're all whatever I feel like running them as. very convenient.
Is the original bad or non-existant? Is the model painted? Is the model cool? Does the model convey the concept? If four ‘yesses’, the proxy is good to go. Albeit, I’ve only proxied two models ever.
My eyesight is pretty shit, so for me guns are pretty much "small" or "big" or a few special cases like snipers and missiles. As such I prioritize specialized weapon type first, armour type (HI or big MI as HI for example) second, followed by a "right sized weapon".
I look to unit type first, followed by Weapon. It MUST have the proper weapon though. If it doesn't then I dont even put it in my list.
When it comes to Infinity, WYSIWYG can sod off, in the nicest, most respectful way. The weapons have inconsistent design elements across factions, and they’re often too small for even experienced players to quickly identify at table distance during gameplay. Many profiles do not have models, CB rarely includes weapon options in products, and the company does not sell bits. So for me it is a ‘go nuts’ situation with respect to weapons. My primary goal is to prevent confusion. If I’m using a model to proxy a different unit, don’t use a model from that unit to proxy something else. Where possible use consistent ‘unit swaps’ or consistent design elements among proxies in the same unit, even if that is a distinct color scheme. My secondary goal is to match the basic ‘look and feel’ of what I am proxying. Hackers have some manner of ‘hacker hand’, skirmishers are lightly armored, snipers have long barreled guns, heavy weapons look heavy. Where possible, use faction models.
While I generally agree with you, that sentence is where I disagree. It's a lot easier to positively remember 'that unit isn't quite what it looks like' when it's not something from the faction (or at least not something from the sectorial you're playing).
That’s a decent point, but I like to keep my Nomads looking like Nomads. Most factions have pretty consistent design beats. I like to try to maintain those.
Consistency and distinctiveness If I'm proxying four Ghazis they should all have some immediately recognizable trait that makes it easy for me and my opponent to remmeber that That One's The Ghazi. If I'm proxying two different loadouts of Muyibs I need to choose models that are easy to tell apart at a glance so I don't get confused. Etc.