Dotted
Dotted is an extremely uncomplicated LEGO font. All it takes is a lot of one part (the 1x1 round plate), patience and a pretty big area to build on. It's built studs up, which makes it particularly suitable for mosaics. If Compact feels to impersonal, maybe Dotted is the way to go.
All letters are based on a 6x5 grid. That gives it an even baseline. When you ensure each letter is separated by at least 1 stud you've got great legibility too.
An alternative might be to replace the round plates with square, but I'd recommend against it. A, V, W and other letters with diagonal lines will look very jagged, which will decrease legibility.
Examples
This is what Dotted looks like written in its own font.
