Using a wallet building service is probably a bad idea, unless you're releasing a shitcoin for quick dump and profit. Options for the coin are probably fairly limited and they're unlikely to offer ongoing support.

0.5 BTC is a fair amount of dough these days!

What exactly needs to be done to the wallet? A fresh and stable build using updated, bug-fixed source, with the network staying as-is, or a hard fork that changes to something like PoW+PoS?