One of my favorite things about Sentinels is it is like someone sat down and took a bunch of characters they liked and said "What would this character be like if we made them more cool and gave them a better backstory."
In my alternate sentinels universe Mr. Fixer dies protecting his students against the thugs, and his star pupil Sophia becomes a vigilante bent on avenging her mentor, after nearly dying in an attempted murder of Pike she is taken in by The Wraith, who helps her focus her anger more productively. (not a sidekick though)
Meredith Stinson wasn't caught in the accident at the labs, and instead several of her colleagues died. Disgraced she ends up working for whoever will let her do her experiments, and comes under the employ of Baron Blade.
Baron Blade after losing to the Freedom 4 (with Sophia replacing Tachyon) gets a message from a desperate businessman who is very interested in helping him, and Baron Blade is invited to join a group of criminals known as the Organization, Pike, without his right hand is weak and it doesn't take the Baron long to take over the Organization and Pike Industrial and use its might and connections to prepare for his vengeance on Legacy.
When the Pike Cryogenics lab catastrophe occured, the head of the research division convinced Baron Blade that she could keep him alive and harness his powers. Deep Freeze is born, and his goal is to strike back at the heroes that protected and perpetuated the system that allowed his fiance to die and her killer to live.
With Meredith Stinson and Baron Blade working together the Baron is much more successful in his schemes, although they take on a much less destructive tone, and are more geared toward control and aquisition.
The Voss invasion gives Baron Blade the perfect opportunity to gain major political power in the States, through his puppet Pike. Pike ends up President, and Legacy and his friends end up fleeing. The process that makes Omni-blade is much more successful, with the help of Dr. Stinson and a promising young associate that becomes Blade's protege, Ms. Caspit. Baron Blade builds his first sentient Defense platform/factory, run by a symbiotic hive mind AI that is convinced god is a girl named Devra.
Heroes around the world, desperate and defeated at every turn by the mechanical Armies and super powered special forces of Baron Blade flee to the one place that is safe for them. Insula Primalis, and the Protectorate of the Citizens of the Sun.