Several of these have already been mentioned, but here are mine:
- Mac OS X support
- iPhone support - There are several ways to accomplish this, the minimum being a .bsm viewer for the iPhone, but ideally it'd be similar to BeerAlchemy Touch but with BeerSmith's feature set. Another possibility is adding the ability for BeerSmith to sync its information with BeerAlchemy Touch. You'd be limited by the feature set of BeerAlchemy Touch, but honestly it'd go a long way toward the goal with very little effort, I think. Another option would be to partner with BrewPal and have wireless sync of BeerXML between BeerSmith on a computer and BrewPal on an iPhone.
- Searching/filtering in ingredient dialogs - A little search field so I can type "dextr" and it'll filter for all matches in the current window.
- Support for split batches - I pretty much always brew a double batch and then do something distinct to each half, e.g., different yeast strains, different dry hops/fruit/spices/oak cubes/bugs in secondary, different fermentation temps, etc. It'd be great if you could design a single wort and then multiple processes for what happens once it's in the fermenter.
- Adding ingredients by proportions - Right now AFAIK you have to specify an exact amount of each ingredient you add. It'd be great if instead you could specify you want 80% to be your base grain, 10% 60L crystal, 5% rye, and 5% unmalted wheat, then say you're shooting for a 1.063 OG on a 6 gallon yield and have it figure out the rest.
- Adjusting hop additions for alpha acids - If I have an existing recipe that uses Cascade with 5.0% AAs and my most recent Cascade are 5.4%, I'd like to be able to tell BeerSmith to adjust accordingly. Even better, it'd be great if you could specify the two primary methods for doing this, one that retains the exact AA contribution of each Cascade addition and one that only adjusts bittering hop additions for AAs.
- Batches - I use the Brew Log feature heavily, but BeerAlchemy has a nice notion of a base recipe and batches of that recipe. Since I re-brew the same recipes often, it'd be great if they were automatically grouped by the base recipe in my brew log.
- Water chemistry optimizer - I use two Excel spreadsheets to calculate my water chemistry adjustments, one that lets you input a base water profile, a target water profile, and a dilution ration and then uses Excel's Solver library to optimize for the salt additions, and the other being John Palmer's RA calculator. In fact, I've combined these into a single spreadsheet (http://www.wells-inc.com/files/Optimized_Palmers_Mash_RA.xlsm) so I only have to add inputs in a single place. Having this seamlessly incorporated into BeerSmith would be huge! I could easily see you selecting your source and target water profiles in a recipe itself, optionally specifying a dilution ratio, and BeerSmith would automatically add the salt additions required based on your batch size.
- Plug-in extensibility model - With a solid extensibility model, most of the enhancements listed above could be added by external contributors. However, getting such a mechanism right can be EXTREMELY difficult, so I'd rather just have a solid version of BeerSmith. This is more blue sky!