First, I am assuming you are talking about 4e.... In 5e we have no idea what the rules for inhabitation will be.
But this is what the 4e street magic book has to say on inhabitation:
street magic page 100, bold by me
INHABITATION MERGES
True Form
When a spirit inhabitation results in a true
form, the vessel is destroyed or consumed during
the merge and cannot be recovered. The
spirit takes form on the astral plane and gains
the powers of Astral Form and Materialization
(see pp. 287 and 289, SR4). A true form spirit
bares no resemblance to the original host vessel
and has the skills, attributes, and knowledge
of the spirit alone. A true form spirit can
persist in the astral plane and/or physical world
indefinitely without needing ties to a conjurer
or a spirit formula. Once disrupted, however,
the spirit requires a new vessel to inhabit before
it can return.
Hybrid Form
A hybrid form is a hybridization of the vessel
and the spirit into a single dual natured
entity (p. 289, SR4). A hybrid form merge enhances
the host’s Physical attributes by the
spirit’s Force. The spirit retains the host’s
natural abilities, though it only has few of the
host’s memories and none of its skills (the
spirit retains its own skills of course). A hybrid
form spirit has Immunity to Normal Weapons
(p. 288, SR4), but loses the ability to assume
an Astral Form (p. 287, SR4). The inhabited
body exhibits signs of the spirit’s takeover, as
the merger physically warps the vessel with
visible telltales of the spirit’s own nature (see
Spotting Spirits, p. 95). The spirit is under no
obligation to return to its metaplane of origin
if/when its services are banished away and will
simply persist as an uncontrolled spirit indefinitely.
Unlike possession spirits, hybrid form
merges can operate a direct neural interface
and the host’s cyberware (if any) continues to
function for the spirit.
Flesh Form
A spirit which attains a good merge with
its vessel becomes a near perfect flesh form.
The combined entity retains all of the memories,
abilities, and skills (both Active and
Knowledge) of the host, and its appearance
is virtually indistinguishable from that of the
original vessel. A flesh form spirit is a dualnatured
creature (p. 287, SR4), has Immunity
to Normal Weapons (p. 288, SR4), any of the
vessel’s natural and augmented abilities, and
also gains the powers of Realistic Form (p. 102)
and Aura Masking (p. 98).
A spirits' Essence is [Force]... so yea... I would say add the two together... Meaning Hybrid forms are tasty to essence eaters
Keep in mind however, once they are merged, I don't think they can get more cyber (can they?!) after all, their physiologies are warped, twisted, randomized genetic material, not exactly "meta-human" anymore. We also know that Ares spent decades trying to weaponize insect spirits..... and we are not too sure what happened there yet....
meaning. you only get the original 6 essence of the host to muck around with augments. you can NOT go, say 5.5 essence worth of augments as a troll, then merge with a force 6 insect spirit, then install another 5.5 essence of augments as a hybrid form.
