Missing out on Colossus will provide a small short term advantage, but I don't see it being able to help in any way related to war with Saladin.
Even if thefrom the missed wonder equates to 500
because of libraries, that only equates to 3 to 4 turns of research advantage due to deficit research opportunity. OTOH completing Colossus will provide for about 10 to 12 extra
/turn. So the research advantage won't last long. It'll only take about 40 or 50 turns for a completed Colossus to outperform the option of losing out on the wonder.
Of course as vanatteveldt pointed out the AIs might not cooperate by building Colossus as soon as Sisiutil stops, so the losing out on the wonder option will actual fall behind the completion option due to the extra/turn from Colossus.
Also the current tech situation doesn't seem to provide a benefit from quick researching of military techs. Sisiutil already has the techs to build maces, LBs and x-bows but his cities are tied up with other builds. Engineering will be done a couple of turns after Colossus would be completed (or put on hold) so the decision won't have any impact on when that tech is acquired. That will add trebs and pikes to the available build options. The only medieval military tech left would be Guilds, which isn't really necessary and it will completed in sufficient time regardless of what happens with Colossus to allow Sisiutil to add some Knights to the build queue in time for the invasion.
So I don't see any impact on a medieval war. And if Sisiutil ends up waiting for a gunpowder war then completing Colossus would clearly be the better option.
Finally there are the other intangible benefits of completing Colossus: the GPPs (with Babylon possibly getting NE at some point) and the denial factor of keeping the wonder out of the hand of one of the AIs.
Now that I am on the Colossuss bandwagon out of support for sisiutil, I have reworked my numbers. My previous numbers were based on Minoan getting the NE and GT national wonders and just pumping specialists the entire game. especially with Babylon surrendering a clam to the iron city. The NEW plan involves Minoan getting the Mocha statues. That will make it a very strong city even after the Colossus is obsolete. Once Mocha is finished it work the pigs, 2 fish and as many coastal tiles as possible while growing to max size. Once it is maxxed and colossus is obsolete it can also work all the workshopped plains tiles as well. Green faces may limit it a bit but it should get close to max size. With colossus and Moomoo statues it will pump naval units fairly quickly as well as bring in more commerce than missing the statues will generate. Perhaps running specialists once all water tiles are worked.
Granted he could run specialists instead of working the coastal tiles I believe 7 is the number of specialist that Minoan will support. But to do that he needs a temple, marketplace and library still if he wishes to stay in slavery for the war effort. If he works the water tiles with Mocha and colossus he has a food surplus of 14 for rocket growth and maybe a little whipping of units as well as the hammers from maeiou statues. 14 surplus food gets him quickly to size 12 which is the number of water tiles he has in minoan alone. That is 12 bonus commerce which means 30 turns to equal the gold from missing colossus. That is just from one city. He has 8 other water tiles that make sense to work in his empire (the others are less valuable compared to other tiles available even with Colossus) For a total of 20 commerce per turn. Even without market and library bonuses that is significantly better than missing it. Enough of an impact to warrant whipping it as soon as it is possible to do so in case some rotten AI is using cheating immortal bonuses to build it.