I agree with your path 1 assessment. To acheive deep bass (say in room flat response down to 30 Hz) from BLHs, the cabinets must be huge and extremely stiff. The practical alternates are to ignore the lack of bass or somehow augment with a powered woofer. IMO many listeners have unwittingly learned to ignore a lack of deep bass or have never heard deep, musical, dynamic bass and so they underestimate these considerations.

Regarding your path 2 discussion: One significant advantage I find in BLH, OB, TL or pipe designs is that they direct the rear wave so as to avoid reflecting back to and through the semi acoustically transparent driver cone to be heard as a time smear form of distortion. Because of this time smearing, I'd love to find more commerically available TL sub options.

IMO the dynamics of one speaker cabinet design versus another is primarily dependent on the driver efficiency. Seems that the confusion and debate of cabinet types comes in due to high efficiency drivers which often have low Qts values and therefore correlate most often with BLHs. And so BLH cabinets are praised when its the drivers that dictate the choice of cabinet designs in the first place. Note that the highly praised and approachably priced extended range Visaton B200 driver offers an alternative to BLHs with it's high Qts and high efficiency.

I'd prefer to see a sub crossover lower than 200 Hz, but am eager to audition Retsel's Lowther/OB.