I'm not familiar with any 'unsyncable wallets'. People have had a couple of issues with simplewallet not syncing w/ TurtleCoind daemon properly, which is addressed by doing a `reset` command in the wallet. There is also an issue related to trying to use a simplewallet-created wallet file in walletd and vice versa. The solution was to leverage the 'walletgreen' code for wallet file management and that is already in testing.

Large transactions can indeed be held up when the balance is a combination of many small transactions. Fusion transactions to combine smaller amounts into larger ones in a wallet, and chunking large payments into several smaller payments, are both solutions. Both are implemented and in testing in GUI wallet.

-bebop