hi ranlo,
Thanks a lot for your proposal. Actually the feature you want is already available

In the Strategy page, if you open the Expert mode you will find a setting called : Keep amount. This setting will block lending under a certain threshold of your balance.
Holding back a % of your balance could be an interesting improvement (thanks!) even if we think that its very important to keep strategies as simple as possible for a better usability and user experience for the moment.
Regarding swapping funds between wallets, it would require to add specific rights in the exchanges API. For the moment we are dedicated to creating margin lending offers on your behalf. We are very cautious with any other API rights.
Actually wasn't aware that was already implemented (the first one). That's awesome and shows we're on the same page!

The %age could just be an addon there, such as "Keep amount: ____ BTC OR ____ %"
On a somewhat unrelated note, are your default settings seen as being a pretty solid setup? I noticed that it's set to only lend at 0.2+ BTC and such, for example, as opposed to 0.05 (I think this would be about the minimum right now).