I would like a monthly/weekly bonus based as a percentage of loss (sort of rakeback)
well that seems to be the most requested bonus because this is something fair for me as well, imagine losing 10k wager and you will be given at least 5-10% of rake back? or even 2% is good enough for me if I wager good in my weekly gaming.
but also if there is a deposit bonuses then it much better having those 2 bonuses offered.
If casinos could agree to this kind of rake back bonus it would have been better, but I don't think so because gamblers will always abuse it and take it for their right to be given,
Am not sure what are you talking about mate because rake back cannot be abused as this requires wagering and you'll have to deposit before gathering good amount of rakebacks .
but this is something intended as promo and not their mandatory responsibility to give back to every lost accunted for on a big loss, but there could be certain conditions they can implement for a gambler to have been actively using their casino over a year, gambles more than 10 times a month and have a specific amount that must have been involved as losses just as you've mentioned, this will be a good idea if gamblers can maintain the whole process involved.
but how can they lure a gambler when they are not responding to each players activity ? imagine a gamblers losing thousand of dollars but the site isn't welcome to give at least small back pay for them? you are not a gambler if you are standing like this.