Deep-penetration & commerce raiding strategy
Since the Manties have always been fond of battlecruisers and the notion of commerce raiding, why didn't the RMN embark on a pattern of deep raids and commerce attacks?
I think some of the answer to this question is probably evident from what I said about above. There were three additional primary reasons, however.
First, the Peeps didn't have as much commerce to raid, their merchant Marine wasn't anywhere near as numerous or economically vital to them as was the case with the Star Kingdom, and attacking convoys and individual merchant ships away from clearly identifiable transfer nodes is extremely difficult. Second, the same units which would have been most useful for raiding Havenite commerce were the ones which were also most useful as Manticoran convoy escorts and as escorts, screening units, and scouting units for main fleet elements. In conjunction with this point, the Manticoran Alliance's losses in wallers, and the necessity to concentrate the wallers which it had available, required it to use battlecruisers and heavy cruisers to provide rear area security. This was something the Peeps could do with that massive force of prewar battleships they had; the Manties, however, had badly underestimated their need for rear area pickets, and they were forced to divert units to cover those requirements, even if the units in question weren't the ones best suited for the task. Or even if the units in question might have been far better suited to some other task like raiding Havenite commerce assuming they could find it.
Second, the Peeps' answer to commerce-raiding battlecruisers and heavy cruisers was battleships. Convoy escorts only have to be fast enough to stay with the convoy and powerful enough to destroy (or threatens significant damage to) raiding units attempting to attack their charges. This was something that the missile-heavy Peep battleships were extraordinarily well suited to (although it hadn't been the reason they were built) at least until the emergence of missile pods gave Alliance battlecruisers the standoff missile power to deal with prewar, obsolescent battleships.
Third, trade between Havenite star systems, while important, was scarcely vital to the People's Republic. The transshipment of critical resources for their military machine, and for their shipyards, was vital, but that sort of materials movement and personnel movement could be handled in a relatively small number of large, heavily escorted convoys. Had it been possible for the Manticoran Alliance to intercept one or more of those convoys in heavy strength, then attacking and destroying the convoys in question would have dealt a very heavy blow to the Peep military machine. Unfortunately, in order to intercept them, the Alliance would have needed detailed knowledge on the convoy's route and planned transit times, and the Admiralty would have had to be able to cut loose sufficient firepower to break through the powerful escorts in question. That wasn't going to happen on any sort of reliable, repeatable basis.
By the time the weapons systems had become available to allow successful commerce raiding by battlecruisers and heavy cruisers against convoys covered by battleships, the strategic situation had changed considerably. In fact, commerce raiding was no longer necessary, or even particularly desirable, once it became possible to execute something like Operation Buttercup. The warships required for such a strategy were far better employed on the demonstrably decisive advance straight through the People's Republic's defensive perimeter towards its capital system and the massive attrition inflicted upon the People's Navy in the process.