Overwhelming the RMN with light units
Sorry, but I've just got to point out that no suggestion anyone has yet come up with for using light Solarian units to somehow fend off Manticoran SD(P)s stands the chance of the proverbial celluloid dog in the infernal regions.
First, because none of them have a weapon capable of significantly damaging a superdreadnought. Their missiles are to light to breach superdreadnought-scale armor and their energy weapons (while packing more punch than their missiles) are still to light to inflict any meaningful damage. You aren't going to get them close enough, regardless of how good their stealth its, to use their broadside weapons anyway, unless you happen to be up against a Manticoran admiral who is not only deaf and blind but stupid, and once detected, their life expectancy is approximately that of the Manties' missile flight time.
(In response to the frequently alluded to events at Tiberian, I would simply point out that even Michael Oversteegen can occasionally be guilty of overconfidence. He had no reason to suspect that he was up against current-generation's Solarian stealth technology, and so he wasn't looking for it. Once his suspicions were aroused and he did start looking for it, he found it fairly expeditiously. So while I'm not saying that Solarian stealth won't be a problem for Manticore, I am saying that it is extremely risky to base analyses of potential Solarian capabilities against alert Manticoran defenders on this single, highly atypical incident.)
Second, there is no way in the world that the Solarian League Navy is going to embrace this sort of suicidal attritional approach. It doesn't matter how big the total Solarian population is, and it doesn't matter how small percentage of the total population the megadeaths you're talking about represent. The enlisted personnel of the German High Seas Fleet mutinied in 1918 at the very suggestion that they might be sent out to face the Grand Fleet again, and their losses -- even as a percentage of the engaged naval personnel -- were scarcely a flyspeck compared to the losses some people seem to think the SLN is prepared to accept and keep on fighting. It takes something truly extraordinary to inspire human beings to willingly, even eagerly, embrace martyrdom, and I submit to you that the Solarian League, with all of its ills, doesn't constitute that "something truly extraordinary." I'm quite confident that SLN personnel would also mutiny about the third or fourth time someone suggested that an entire fleet should go out and allow itself to be massacred for the greater glory of Frontier Security and the League bureaucracy. Not only that, but the attitude of the typical Solarian in the street, whose support would be essential to any strategy willing to suck up that sort of losses, is a lot more likely to be that a war with Manticore represents absolutely no personal threat to him or her. Why should he support a war against someone light-centuries away who isn't posing any threat directly to him or his?
I'm not saying that propagandists can't spin the events of a war between the Star Empire and the Solarian League into something closer to Pearl Harbor than the invasion of Poland, but it's unlikely to succeed in any such attempt unless the Manties do something outstandingly stupid to help them. And don't forget that, via Beowulf, Manticore's propagandists have even better access to the Solarian League's capital world (and its population and news organizations) than Frontier Security. Coupled with the fact that the Manties will be able to present the truth as their best propaganda, OFS and its cronies are likely to experience just a little difficulty selling that kind of war to the League. And unless they can somehow convince the Solarian public that the vile, evil Manties want to carry out Eridani Edict violations all over known space, then motivating that public -- and its military personnel -- to suffer thousands upon thousands (or, more likely, millions) of casualties against an opponent whose weapons outrange their own literally by light-minutes is going to be problematical, at best.
If you want to come up with a way for the SLN to mount any sort of sustained operations, except purely in defensive mode, against the Star Empire and its present or potential allies, you're going to have to do better than this.
Unless, of course, you try tum-te-tum-te-tum.