As the system works now the base will go 25% 18 hours after you placed the CT, it will be 25% for 5 hours then change to 5% for 1 hour and then back to 100%, and then the 18 hour countdown start again.
Many guilds are EU only or US only or atleast have most members in 1 time zone, so they need the base to go 25% during that time so they have some chance to defend it.
It's a 24 hours cycle so FC must have ment us to have the base go 25% when we have people online and not just at a random time.
Only way to do this now can very easly be exploited and will also make the base 100% longer than 18 hours in a row and that is not fair.
Only suggestion I can come up with to get rid of the problem is:
1) When you place a CT, you get a timer up there you can decide from 1-18, that's in how many hours the base will go 25%, so if you place a CT and the 18 hour until 25% is really bad for you, you can choose to make it go 25% sooner at a time that fits better.
2) If you terminate a tower to let another guild place there instead(when a base drop, the guild that can place usually place a tower to prevent any ninja to place and then transfer to right guild after) they will get a timer up and can choose between 1 and the number of hours it would have been left for the old CT to go 25%.
3) After a base go down, change so all guilds that are on same side that the guild that lost base have to wait 1 hour before they can place (to get rid of bases just getting ninjad back on same side and given back to the guild that lost base)