All attraction involves the brain. The brain is responsible for consciousness, perception, and motivation.
Not all attraction is physical. In two structural theories of love with which I'm familiar, physical attraction corresponds to a minority of what constitutes love. Love isn't exactly the same as attraction, but much of these theories' content implies attraction that is more than sexual and sometimes not sexual at all. In Sternberg's triangular theory of love, passion often entails physical attraction, but the theory frames intimacy and commitment as somewhat independent and based on other aspects of interpersonal relationships such as trust, closeness, benevolence, role identification, and cooperation.
People have many reasons to desire these relationships besides sex. Lee's love styles considers physical passion a defining aspect of only one of six styles. Other motives drive the other styles: power, affiliation, teamwork, emotional fusion and obsession, and altruism. However, one might argue that some of these are not clearly approach motives (mania in particular may be more fear-driven), or that the other person is more a means to an end than the object of desire (particularly pragma and ludus). Regardless, storge and agape are clearly more platonic (though not necessarily nonsexual) forms of attraction with a person as the primary object.
Separating the mind from the body is not possible at present within the scope of mainstream empirical science. Hence all questions that depend on this premise are very likely to be speculative and controversial, and probably off-topic for this site, which discourages opinion solicitation. Even so, the logic of these theories seems to indicate clearly enough that while many aspects of attraction do not depend on sexuality, some do, and that much might change if the physical object of sexual attraction changes. Furthermore, many physiological elements that influence the brain during attraction would have to be emulated in the alternate host to have unchanged consequences, such as adrenalin, which is produced in glands atop the kidneys. Dopamine and serotonin also play important roles in love style variation (see the reference below); their influence would require emulation as well if the mind were somehow separated from the physical sources of these neurotransmitters.
Emanuele, E., Brondino, N., Pesenti, S., Re, S., & Geroldi, D. (2007). Genetic loading on human loving styles. Neuro Endocrinology Letters, 28(6), 815–21. PMID 18063936.