- Yes… wide front, narrower rear is super common for BMX (many decades of that as a standard practice) and something I continued for MTB setups.
- As a rule for off-road setups, I tend towards having more traction on the front with less in the rear.
- This can be covered via width with similar treads on both ends.
- Or it can be done via different tread patterns on both ends (smoother rear, grippier front).
To your specific issue, the basic concept is fine and will lead to better traction on front from the width, all things considered. But, as you note, the smaller diameter front wheel will lead to changes that may be detrimental to handling.
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Lower front axle will steepen head tube angle, which might counter the grip you gain from the tire, by making the front end more twitchy and fast steering.
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Trail will likely decrease as well, which will lead to a faster steering bike with less “centering” action at the bars.
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Lower front will also lead to more weight load on the front tire, and lower hand position relative to the saddle, assuming you don’t touch any other setting on the bike.
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Bottom Bracket height will drop a tad too. Maybe not enough to cause crank clearance issues, but still worth a look.
All this is theoretical, and hard to pin down without actual diameter differences. The real numbers may lead to a relative non-issue.
Also. keep in mind that measured difference without loading (tires sitting loose) is not representative of under load (you on the bike). So if you want to really know the differences, it’s best to measure axle height when on the bike with appropriate pressure in each tire.
As a general idea, a reverse mullet is not a direction that I would consider using.