I think it’s a very good question, and one that I’ve reflected upon when I lived in remote regions or localities wherein practising Christians were uncommon and services rare.
While the Eucharist is the ‘source and summit of Christian life’ (per
Lumen Gentium), I’m not sure how helpful it is to conceptualise it separately from other aspects of Christian life: the Eucharist is a liturgical act, offered with reverence that directs the physical senses of a person towards God, and it is in the Eucharist that one participates in the Body of Christ, the community of Christian believers.
Regardless of however uncanonical or inappropriate it may be, my impression was that intercommunion (or, at least, Catholics attending Protestant services and vise versa) was quite normal in many remote Australian regions wherein one’s own parish may offer Mass/Holy Communion only once a month. Likewise, intercommunion between Catholics, Eastern Orthodox and Oriental Orthodox in sparsely populated Middle Eastern regions is
a lot more common than one would think (or prefer) it to be.
I suppose what I’m trying to say (in a reflective but probably convoluted manner) is that while the Eucharist is the
fons et culmen Christianae vitae, apparently for many people it isn’t the
esse: that is, Christian life can’t be reduced to the Eucharist alone.
Prior to my living in a major city where my local parish is vibrant, orthodox and reverent, I lived remotely wherein the parish was unfortunately very stagnant. It bore many of the characteristics that you described in option (a): minimal attendance, non-existent parish life, liturgy was not irreverent
per se but very perfunctory. In short, it was the Christian life with the Eucharist but without everything else, and I have hard a time imagining that sort of life is sustainable or conducive to growth in holiness over time.
I don’t have a simple solution for your problem. I personally didn’t choose (b), but I can
understand why one would choose (b) whether it was Protestant, Eastern Orthodox, Oriental Orthodox.