I wouldn't call it modelling for advantage at all. I'd call it buying some minis, then the design changes, then the none Tau player decides to be a dick and the Tau player is completely justified in packing up his minis and walking away without a single word.
You want me to go and buy the new kits, sure can I have your credit card then? I'm not paying to replace the kits I have bought assembled and painted. I mean FFS if the opposing player is going to be WAAC, that butthurt over it and that much of a fucking child I'll get a piece of paper and cut out a silhouette of the new ones and whenever they want to take a shot then I'll hold up it behind the older Broadside. I'll also call them a prick to their face and fight them on everything. Their measurements better be perfect, their knowledge of the rules impeccable and if even a single mini of theirs is converted to outside the norms of what a normally assembled mini would be then well they better get out the paper silhouettes as well. Fairs fair. It's those type of people who ruin the game.