You're both getting right at the heart of this problem and why this hasn't been offered yet as a commercial product. Although, luckily it is a bit more of an engineering problem than a physics problem--this process works, but you need a high intensity single-mode beam. With the advances in diode technology and the current state of affairs we though this would be a good opportunity to asses how viable this approach is currently.
Jors, we actually are exploring the different 450 nm diodes for this and you are right the poor beam quality of these high-power diodes is not ideal for SHG. One of the first things we want to do is first measure the M^2 values of these diodes and then see what power is in the fundamental TEM00 mode by spatial filtering the output. The SHG conversion process is actually more efficient around 450nm than 410nm, but as Cyparagon posted there might be more power in the fundamental mode for the violet (Blu-ray) diode than the high power blue diodes.
There are a couple other tricks we have to potentially increase the conversion efficiency.
