Since doping periods take place out of competition the solution is simply to force the sprinters to compete all the way up to championsships and be tested every week, let's say they all have to compete at least once a week over the last three or four months before worlds just to be qualified.
Lower the qualifying time to 10:00 or 10:05 and enough with all these 11:50 guys from Lower South-East Timor and The East Gagnam Peoples Democratic Republic, if there's just 10-15 guys remaining to begin with come final day at Worlds that's just fine.
Sub-10:00 sometimes over the last two years and you're qualificed for and obligued to join the pre-champs circus, No result sub-10:00 over the last two years, sorry then...
You don't see football teams sit out the early season and decide they don't wanna face serious competition before the playoff/superbowl. They play the qualifying weeks or they don't get to go.
Hell, Japanise Sumo Wrestling has SIX world champs a year (ok, they don't call them that, but that's what they are) and each one lasts for two weeks - champs actually has to pull off the equavivalent of a 10 seconds max effort 6x15 times a year!
That's a second possible solution, have World Championships every other month! It could be done by separating all the events to play down this totally unnecessary "host city" for all the events at once every second year BS
Just imagine, we'd probably have at least one Track and Field Worlds champs somewhere every weekend!).