I get that half is easier to calculate Osle, but as proportions go, it is exceedingly harsh on some stats and not so much on others (again, Great Plating comes to mind).
Being able to go nova on your opponents is a lot more useful if you can ensure that A) you go first and B) they die either during said nova or shortly after. If either condition is broken, then the drawbacks become untenable - you can't go nova if you're dead, and you can't finish them off if you're spent. Given that there is pretty much no way to manipulate initiative within this homebrew system (that I can see anyway), then as a build choice, it becomes a lot less valid.
I imagine that the reduction applies on top of your "current" totals, rather than atop the totals at the time you pick the option (which would make said options a lot more attractive at lower levels), but it might be a good idea to add a note for the sake of clarification. Cthulhu knows us min-maxers hunt for technicalities like they're the last dodo bird.
My suggestion for Tek Reactor, if you MUST apply a reduction to Spirits (I personally dislike the idea of permanent changes to stuff you can only gain through levels... but I get where the design comes from) is to apply a 20% or 1/5 reduction instead. It's severe enough to matter without completely inutilizing higher-level spirits usage (it only delays them). Similarly for Tek Soul, apply a 20% reduction to max HP. Which again, is pretty nasty, but a lot more survivable than 50%.
But Hyperdimensional Storage already forbids Nanomachines and Mysterious Reactor. As it is, you can take Tek Storage AND Hyperdimensional if you want to cram more weapons into your tiny robot (which brings this to mind)...
Now, HS can be taken multiple times, but Tek Storage only once. If you lift the restriction for Tek Storage alone, you provide an alternative for smaller Supers to have a little more arsenal space while also having more staying power. At the same time, if they want MORE DAKKA they'll have to sacrifice staying power for it, which would balance it out. Hyperdimensional Storage still wins out in the cost-benefit department though.