Keep the game alive your way, and if this means using new sculpts then please do.
I am fully in agreement with using modern kits for
WHFB, new modesl mean higher quality standards most of the time. Best example here are the new greater daemons. My Great One One fits on a custom 100x100mm base in 3mm board, I even bevelled the edge so it looks more in keeping with the
GW bases. I do not care there never were 100x100mm bases it fits my fatty. Anyone who disagrees is a confirmed 'that guy', that is universally accepted because I am clearly not modelling for advantage but maximising rule of cool with the plastic Great Unclean One.
I bought some Plague Toads, non Forgeworld ones that need 50x50mm bases to fit. in either case I use Beast of Nurgle rules for them. This is somewhat more questionable so no 'that guy' status for you if you dont want to play them, but nobody complains because again its not modelling for advantage and it fits rule of cool.
One of my Heralds is on a Palanquin and sits in a Plaguebearer unit, the model is a slightly less cultivated looking Horticulous Slimux, more combat mount, less Farmer Giles.
This requires a 50x75mm base, so it has one, I still call it infantry under the palanquin rule and he still hides in a unit of Plaguebearers. Now you could argue an advantage over the 40x40mm base in that it takes up the footprint of six Plaguebearers, but it fits neatly is a no fuss model and applies rule of cool, so I get zero complaints.
What applies to my Nurgle Daemon army applies to many others, but its a more clear application here as I use some non-
GW models and modern
GW models that have obvious parallels to existing models but dont fit on the same bases. My Nurgle army is a joy and I am not trying to cheese anything.
Motive is everything, if you have new sculpts you really want to field, but dont fit existing bases make do as you can and will. The new Black Coach is a case in point, superior sculpt but a vastly bigger model to the original, even though the scaling is appropriate. This model requires a basing standard all of its own, 50x200mm fits to get it any smaller requires creative modelling such as arching the train tighter, and even then requires 50x150mm. You could reduce the horse team, but why should you. The model is awesome do as you will to keep it if you want to field it.
The recently released Slaves to Darkness models also come to mind strongly here. Then you need to convert carefully or apply a new basing convention. Now the new Slaves to Darkness boxset will be a difficult choice, yes they look very dynamic, but they will be hell to rank up. Frankly I decided to avoid this challenge and will not be using this kit for my Warriors of Chaos army. Yes they look new and superior sculpts, but I dont think the workload to make them servicable for
WHFB is worth it unlike my Nurgle and Nighthaunt models. Your time skill and focus will make the primary difference, no point planning a new look army if you wont get around to it or don't have chops for necessary conversion work. But do not allow that guys' to be a factor.