Yeah a step up from a pen style vape would be a small MTL setup, maybe a tube style mod. Many folks swear by the Innoken T18 or T20, it's fixed wattage output and you'd probably get more vapor but maintain the "Smaller" form factor and there are other such options, Joytech makes one for the Ego Mega Tank, for example.
But I'm a bit confused because it seems like you are asking your pen style vape to perform in a way it JUST doesn't do. If you like your sub0hm setups and your pen for stealth, well you could certainly keep that, and bring a sub0hm setup with you for when you have breaks and etc. and use them then, if you prefer the vapor output and everything else.
What you are NEVER going to be able to do is to transform your stealth vape into a cloudy vape, not with a pen style vape, it just doesn't work that way.4
Anna