I know everyone isn't a developer, but this is the beauty of open source software. Grab the sources and learn how to hack in the changes you want personally. If you think they might be helpful to the rest of the community, submit back your changes to the main developers. I'm sure they are swamped and any help would be appreciated.
I'll start and show you how to do this. If you click on the link for the "let users select their wallet" request, you'll see that a patch has already been submitted. If you click on the "Files Changed" tab, you'll see exactly which 4 files were updated and exactly which lines of code were changed. The lines with the "-" were removed and the lines with the "+" were added. Using your favorite text editor, you can make these changes.
So, for the first file, for example, the source code file "src/init.cpp" had one line added near the top of the file:
" -wallet= " + _("Specify wallet file (within data directory)") + "\n" +
This line is part of the command-line help that's printed out.
Next, on line 908, this code is removed: "pwalletMain = new CWallet("wallet.dat"); " and two new lines are added in its place:
strWalletFile = GetArg("-wallet", "wallet.dat");
pwalletMain = new CWallet(strWalletFile.c_str());
(Don't add the + or - signs at the beginning of those lines, by the way. They are there just to show you that it has been added or removed.)
Next up, on line 971, this line was removed: "CWalletDB walletdb("wallet.dat"); " and this line was added in its place:
CWalletDB walletdb(strWalletFile.c_str());
Ok, follow the same directions for the next three files that need to be changed: src/main.cpp, src/main.h, src/qt/optionsmodel.cpp
After you make all of the changes, you'll have to compile it to make it an executable program. The file ./bitcoin/doc/readme-qt.rst has the simple instructions for doing this (you can read it online at this link:
https://github.com/bitcoin/bitcoin/blob/master/doc/readme-qt.rst)
When you compile it with the "qmake && make" commands, it will tell you if you made any errors adding the lines above. If you see any "Warnings", you can safely ignore those. The program will still compile and work correctly, they are compiler warnings. Any "fatal" errors, however, will stop it from compiling.
There you have it. Keep in mind that you are now using your own custom bitcoin client. Any updates that you need to do, like official security updates, may break it and you'll have to grab the new source, add your changes and recompile. So there is that caveat.
Hope that helps. It's a bit arcane for non-developers, I understand. Bit the more you get your hands dirty, so to speak, the easier making these changes for yourself will become.