It all depends on what sort of mashup you want exactly. Keep in mind that some of the official cornes have a break-off 6th column so you can get close to the same key count as a Sweep (36 instead of 34). Here are some that might come close.

• https://github.com/jimmerricks/chocolad
• https://github.com/...
• https://github.com/...

I use a 30 key keyboard and do not use homerow mods. It is definitely possible. I use mods on a layer. Callum (sticky) style mods on a layer are also an option. You can see my layout here: https://github.com/jcmkk3/zmk-config

Do you mean one 2u key in the middle instead of the two? If so, that's an option.