I am quite curious as to what kind of risk/expose are there for the exchange to provide such feature?
I don't actually know, but I assume not. If I understand correctly that would expose the exchange to intolerable risk.
the conditional close from Kraken has of course no risk.
Maybe he also thought, that the OP want to place orders completely without bitcoins and fiat.
But this is also possible at some exchanges in the one or another way.
1) bitcoin.de allows you to place sell orders of bitcoins which can stay in your own wallet. Of course this trade offer is marked and I did not see a single one in the market, because it is very time consuming (buyer accepts sell order, seller has to send the bitcoins to bitcoin.de, after that the buyer sends the money ...)
2) bit-x allows to use your balance more often. If you have 1 BTC at bit-x, you can place a limit sell order for 600€ about 1 BTC, another one for 700€ and another for 800€ and so on. That's why the orderbook of bit-x is quite full (for being a very small exchange). To prevent the users to place too many orders, you have to pay a fee for placing an order. As soon as the first of the sell orders is filled, the other orders will be removed from the orderbook.
I know, this does not make any sense (because of course the 600€ order is filled first)... but this is how I understood their orderbook. You can read it here (unfunded order):
https://bit-x.com/guide/funded-unfunded-and-on-hold-orders.. maybe when you have several unfunded orders, and then deposit more, they will become funded. But I think it is not worth to pay a fee for placing an order.