This suggestion is mainly to Protect your 31 speed Pokemon. Most of the Pokemon anyways that will want the specific Hidden Power are sweepers and the lack of 31 speed can quite often ruin them. With a cost that is reasonable (needs to be relatively big) you can pick the IV you want to keep as non changing. If there's no possibility for this, for example you cannot keep your certain IV as Odd/Even in order to get the certain Hidden Power then this obviously isn't possible. But when it is possible I think this feature makes you utilize the Hidden Power selection feature the best way as speed IV is important often to be 31 for sweepers to make a Pokemon competitively usable.
Pros
- Make 31 Speed Pokemon be able to utilize the Hidden Power feature
- Additional Money Sink
- Well you basically are giving us an option to choose a Hidden Power but this limits it quite a lot
Cons
- Make stuff too easy?
Anyways, discuss.