If Tsarism had survived WW1, I believe Olga would have made a royal marriage....or at least one acceptable in that context. There was a practical side to this dreamer....just as Tatiania had a " whimsical " bent according to some. Their natures were not set in stone. They could surprise those around them. Olga was very aware of her duty to her county and her parents and would, I believe, have made a marriage they found suitable. And it's to be remembered they were sticklers for marriages deemed correct ...they had very decided opinions on that.
But Tsarism did not survive and so I don't think one can say what would have happened, besides to say Olga Nicholaievna would have married: she wanted that. Olga told her fellow nurse, Valentina Ivanovna Chebotaryova, that her big dream was to marry ,live always in a village and with no formality...well by that time the war was already changing Olga's world and the world at large. I believe in the spring of 1917, Olga had hopes of a wider field of choice, that just a short time before seemed impossible.....Her parents allowing Olga Alexandrovna to finally marry the commoner she had loved for years , was a bit of an earth quake...even before the Revolution . But sadly Olga Nicholaievna's hopes, whatever they were, were not to be realized.
I do not think Nicholas and Alix saw their daughters as royal chips to bargain with...but they were not adverse to seeing if something could be made of an opportunity. All I know is they took Olga to Romania...and it wasn't Olga's idea. However if Olga had insisted on someone suitable, I believe her parents would have agreed...but it seems in 1914 she was not ready to do so...and afterwards the war and captivity made marriage to anyone impossible.