From the Git:
8683df2: Implementing withdraw_address setting: your btc address you want Gunbot to withdraw your profits too. WARNING: optional and dangerous setting. It needs RESERVE_PILE_UP set to true, withdraw permission at your exchange API settings. You can set a threshold using withdraw_threshold setting (example if set to 1, gunbot will withdraw to your address when you pile up 1btc of profit from your original invested capital). Despite this setting is useful to actually see profits in a more real way, i highly suggest to USE THIS AT YOUR OWN RISK).
So, no: I don't think this setting is what you're looking for...
Which leaves us with the question :
HOW can we tell the bot that what we want to do is NOT accumulate BTC, but accumulate the ALT of our pair instead...