I find it refreshingly simple.

This is a really good start! With a comic-focused Patreon, I've seen people use a couple tactics to bring the most to their patrons.

-Low-level tier, $1 and/or $5, is generally where the basic comic starts, with additional doodles/studies being uploaded for the non-$1 patrons.
-For a mid-level tier, I've seen a lot of people do the "Steering Committee". People vote on different ideas by you on how to advance the comic/characters, or offer their own ideas.
-For a high-level tier, eg $20-$40 and above, you could offer the opportunity for patrons to have cameos in the comic and/or other personalized opportunities. Discounts on art, streaming preference, etc. Although that really depends on how many pages you'll be able to complete per month.

Not terribly different from what you've got going on now, but just some clearer differentiation between the tiers may help a bit. Mylifewithfel/Kennoarkkan and Jay Naylor both have really successful comic-based patreons, so I'd suggest checking them out for any ideas as well! I hope this helps!