Hello,
There is a eWay rapid plugin created by Obsidev two years ago :
github.com/HikaShop/hikashoppayment-ewayrapid
Yes, with some development it is possible to implement the support of the pre-auth and be compatible with the authorize/capture system of HikaShop core.
That core feature allow to make an authorize on order creation and perform the capture when you modify with a specific order status, generally "shipped".
Since it would be a custom development, it would be better to contact a developer to get a quote :
www.hikashop.com/home/our-partners.html
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.