size 16 prescripted world. this means that you'll have to move your capital later on...
Fair point this is worse now that not all staring worlds are size 16.
Climate Restoration (the tech you need for Tomb Worlds and to terraform the "Terraforming candidates") is currently marked as Tier 3 tech. That is late game if I ever saw it.
On the timescale at wich Mars becomes "habitable", habitats might have been in service for decades (if you go that route) or you already have 2-3 sectors.
Terraforming Mars is a nice little fluff thing with no danger to game balance at all.
With stuff like having Trappist and it's 3 habitable candicates spawning? There I could see a real danger for game balance from the human start.
Adding primitive civilisation planet - possibly even totally different habitability - is a whole nother story altogether. Especially as the chance of being noticed during the annexation is non-existent.
I could see it comming as part of a Civic, maybe. If the Planetclass was fixed (same as yours or at least same Climate Class as yours), to avoid just throwing you a whole new class of planets to grab. Or if they were backwarsd like Iron Age (at wich point Culture Shock takes 100 years to overcome).
But throwing you a primitive Civilsiation with all risks of invasion negated?
There a major disconnect in your argument where you seem to think that the fact that it's better than Sol means it's too strong. This might work if your argument weren't that Sol isn't particularly strong, when other examples I gave which were stronger to begin with and also cost nothing are ignored. I will concede that Sol is a bad example, but why is a chance of getting primitives within your start system (this) so much more OP than getting primitives within your starting borders (normal RNG thing which already happens at gamestart) that it needs to cost a permanent policy slot?