Well sounds like you are on a mission...
An additional item of consideration is the strength of the gimbal motors. The newer ones are made stronger so that if you want to add an attachment lens to the smartphone the gimbal can handle the weight. For example I have an anamorphic lens that I sometimes use on my phone. The gimbal can handle this additional weight. FeiyuTech Vimble 2S is inexpensive and also includes an expandable stick to give you a bit of extra reach.
There are also a lot of different companies that make some cool inexpensive lenses. I would consider having a non permanent case so that you can experiment.
Clear as mud right...
Sidd