Would love to see some of the mid-tier Sailors and Pilots. I love the nibs from these companies. The M-F offering from both is my sweet spot. 823's, Custom 74's, 1911's, Realo's, Pro Gears. Unfortunately both of these companies adhere to very strict selling programs - to the point where grey market may be an issue for this Platform.
Stay away from the kit pens - the sections are predominantly too thin and too slippery to be used for longer writing sessions.
Note-takers are best served with a snap cap (my favorite of these is the Faber-Castell essentio) - twist caps are better if the pen will be uncapped for longer writing sessions.
Be wary of too many Jowo & Bock nibs - these companies supply the majority of nibs these days, and from my perspective this makes things a little boring.
While I don't drool over demonstrators, I do like to see how much ink is left in my pen. Staining inks make short work of demonstrators, whereas cartridge-converters can be easily (and cheaply) replaced. The downside is of course ink capacity.
I will buy an Aurora 88 some day, but probably never a Visconti or Montegrappa. It's a personal thing - too many of the Visconti's have too much bling, and they've been cursed with poor performing nibs right out of the box for too long.
I'd like to see some Tomoe River notebooks offered, along with other fountain pen friendly options. Rhodia and Clairefontaine make great things to write on, but a little more diversity would be nice. Kokuyo, APICA, Midori, LIFE, Tsubame, etc.
Would also love to see more ink vendors in play. The recent past has seen the launch of some excellent ink manufacturers and I've yet to see these (perhaps I've missed them). Pilot Iroshizuku, Pelikan Edelstein, KWZ, Robert Oster, Colorverse, Kyo No Oto, Organics Studio, Platinum, Blackstone, 3 Oysters, etc...are but a few that may serve to spruce up the ink selection here on Massdrop. And there are a ton of others that deserve mention here also but their names escape me.