That's frustrating, because the idea was that it could bombard twice with its weaker attack or repair units but has slow movement. Not sure how to circumvent the movement -> action requirements. I suppose it could have 2 movement, attacks cost 1 action, movement cost 2 actions, and repair actions cost 2 actions. That's a nasty workaround, but it could work.
So the fortress would be a great admiral... that doesn't suck?
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Well basically, it would be an (almost) unkillable great admiral that can do some damage itself, and only helps Defend units rather than boost their attack
I don't think a lot of people would be happy with that range. Sea units do have more speed, but they still have zone of control. Revising my former statement, I would not make it longer than 6 tiles range.
I guess if was 5 initially, and then 6 in the upgraded version it could be interesting
As for explorer ideas, some of the abilities need to come out Early to matter... So I would say No 'non-affinity upgrade'
Instead upgrade at level 4 with core affinity (early enough to get anti alien defense/immunity to miasma)
Then upgrade at level 10 or 6.6 with core OR hybrid
so perhaps
Explorer->
True Explorer/Prime Explorer/Evolved Explorer->
Pioneer/Savant/Missionary/Errant/Druid/Paragon
As for what they can discover...
I'd go with a 2 step, each one has "hidden sites" specific to their affinity.
Each hidden site when processed gives artifacts (Purity->OE only, Mastery-> OE or Progenitor, etc.) once the site Gives the artifacts, it becomes a Different 'hidden site' that the 'explorer' can put an improvement on it
Purity-Culture, production, health
Ascendancy-Production, culture, food
Harmony-Food, production, science
Audacity-Science, energy, food
Supremacy-Energy, health, science
Mastery-Health, energy, culture
[big amount of capitalized one, lesser of the other two, actual amount depends on what it is "Science" ~4 science, "Energy"~12 energy]
For other stats, I'd say
Explorer-6 strength, 40 prod
lvl 1-12 strength, 120 prod
lvl 2-22 strength, 240 prod
Harmony1
base abilities: can leash aliens, immune to miasma
options: greater leash ability (take less damage) OR +1 move
Harmony2
base abilities: "hidden harmony sites", +1 move +1 vision
options: heal +10 hp every turn ended in miasma OR no ZOC, +1move
Supremacy1
base abilities: +1 module
options: +1 vision OR +1 module
Supremacy2
base abilities: "hidden supremacy sites", +1 move, +1 vision
options: detect invisible units OR enemy units in visual range take a combat penalty when attacking your Other units
Purity1
base abilities: + defense v. aliens
options: +offense v. aliens OR +10 heal outside of friendly territory
Purity2
base abilities: "hidden purity sites", +1 move, +1 vision
options: can build regular worker improvements/actions at +50% rate OR +5 hp heal every turn
Mastery
base abilities: "hidden mastery sites", +1 move, +1 vision
options: detect invisible units OR +5 hp heal every turn
Audacity
base abilities: "hidden audacity sites", +1 move, +1 vision
options: detect invisible units OR no ZOC, +1 move
Ascendancy
base abilities: "hidden ascendancy sites", +1 move, +1 vision
options: no ZOC, +1 move OR +5 hp heal every turn
the +1 move from the advanced also includes a +1 embarked move
each type of "hidden site" would only appear about once every 50 tiles (which means 1 of some type about every 8 tiles, but you can only ever see 1.)