I"d suggest you rent it before buying it.
A 7mm will limit your mobility greatly, in mi opinion, more than with a dry suit. The original post states that a dry suit is something you don't want or need.
Again just my opinion, but maybe you should approach the situation in a more objective fashion. There are many types of dry suits, a lot more than 7mm wetsuits.
Take your time and try them yourself. Talking about it is truly not that useful, unless it is about how best to entry/exit, maintain or similar.
Cold tolerance is so very personal, for some people 10 degree change means a slight discomfort; for others just 1 or 2 degrees makes a huge difference. Diving in South Florida I use:
thin cotton mechanic coveralls,
skins with polartec inside,
3mm wet suit,
3mm wet suit with hood,
3 mm with the polartec skin inside, hood and booties,
dry suit with thin undergarment,
dry suit with very fat undergarment.
I dove with 5mm wetsuits and hated the movement restriction, I put on a 7mm once and removed it right away.
Maybe a 7mm is the best choice for you, but before investing on one, do yourself a favor and check all your options.