I have a crossfire 3 converted about 6 years ago with an Ezee front hub.
I have converted the front disc to hydraulic, with a larger disc, to handle the extra speed and weight.
Firstly, 25-30 mph is too fast. The forks are not good enough and, being a hard tail, at those speeds you will get shaken and juddered to pieces. Also braking and tyre grip will not be up to it in high traffic situations. Will it stop when Mr Dick Head does something unexpected/stupid/well it's only a cyclist.
At 25-30 wind resistance is significantly higher especially as the crossfire is not an aerodynamic road bike. You would need a battery capable of delivering a much higher constant current and therefore higher capacity = more expense.
My kit will sit at around 14-15mph in setting 3/5, at this it takes around 40 minutes to do the 9+ miles to my workshop. (Rural Wales, no traffic lights or, indeed, any traffic) But this speed is too high on some road sections with poor surface and I drop to 2/3 giving around 12mph.
For commuting I would recommend a rear hub for reliability and ease of ride and fitting.
Choose a geared hub 250w rated. I would not choose an apparently high rated hub (1000w or 1500w). Though cheap they are direct drive give high speed on the flat but are crap at hills and eat batteries. As well they are, of course, illegal which may be a consideration in high population areas where mishap/accident is more likely.
What you want to do is very achievable if you alter your speed expectaions to 20mph max. Depending on your age, weight, terrain etc. This is doable by you (with some effort) on a fully legal kit. Cut off speed will be around 16-17mph with you putting in the extra, especially as fitness level increases.
Have a look at Woosh kits as a start.