If the conversion keeps you cycling, I don't see that ideology or even religion comes into it.
You may be somewhat limited if you want to keep a Rohloff or derailleur setup at the back, and the eccentric bottom bracket keeps you from using a central motor with a Rohloff, unless you want to add some manner of chain tensioner.
You used to be able to get rear wheel hubs with clusters of gears on them for derailleur use, and may still, but they were the most unsophisticated of all the early electric motor installations but also the most brutally efficient. I mention this because theoretically a rear installation reduces the mess of wires that are -- believe it or not -- the biggest practical bother about fitting your own conversion, and can also be ugly on a careless conversation commercially done. Note the "theoretically"...
All of that said, the easiest fitment and the easiest wire-tidying job among my electric motors has been with a full kit from the British Bafang/8FUN importers for the front wheel. By contrast, fitting the Bafang/8FUN central (bottom bracket) motor was a nightmare even with some of the electronic gubbins contained in the motor case itself -- until I got smart and instead of trying to wire tidily, I started thinking laterally and simply folded and refolded the surplus wiring until it would fit in one of those office computer spiral tidy cables, which conveniently come in neutral grey and black. I had the grey and that fitted well with my BRG bike. All of this par may sound a bit over the top, but it's the trickiest part to get right if you're getting on a bit and trying to limit bending over the bike. It isn't any more difficult really than fitting an n'lock (which nearly gave me a stroke the day before going in for heart surgery) or getting a Chainglider onto the chain and gearwheels the first time without ripping it apart or tying it into knots.
Here are some tips, discovered to be important by the questions people on the British pedelec forum asked me either on that forum or to my private mail:
1. Yes, you can fit any position electric motor yourself (as wheel hubs rear or front, as a centre motor), if you have a full kit, otherwise you risk an unfinished project. This is given on the assumption that you have removed and replaced a wheel and a bottom bracket before, and that you know that electricity flows in two or more wires which are different, usually not only in function but in colour.
2. I believe that in the UK there is a power limit on the size of motor you can use on the public roads. You must absolutely be satisfied that the low-watt motor you are forced to buy has high torque, or it will not be satisfactory. This isn't as difficult as it sounds because there is no standard by which pedelec motors are measured: the authorities take the word of Chinese(!) manufacturers, people who've been trained by their government on threat of existential penalties to tell them what they want to hear, a skill easily transferred onto customers! One reason I stick to Bafang is that they have a lot of experience with high torque motors from the years when the BPM (a hillclimber as in competitions) was their big seller, and the UK-legal Bafang motor I had on the front wheel first to give me some perspective on a new field is commonly referred to as "the little BPM".
3. A common complaint from the people who stop me on the roads or in the supermarket to ask if I want to sell them my bike -- which is clearly by its longevity (it's now thirteen years old) a riotously successful installation -- is that the electric bike they have, which stands idle in the garage, doesn't carry them further than the shopping. They've made the three most common newbie errors in electric bikes: They specified the battery too small, they expected the battery to do all the work, and they didn't look after the battery. I've never once run my battery for more than half its storage capacity, I charge the battery the minute I get home, even if I rode only a kilometre to the shops (I find that these days I'm better balanced on my bike than on my feet), and I specified the battery at a humongous 14.5kWh, at first glance far outside my requirement, but in practice hardheaded common sense and careful calculation from experience. My first battery, from the trial front wheel installation, is still running and good, probably fifteen years old, and would have been enough for normal rides on the new motor, delimited by how soon we run into a river at a quay somewhere, where there's no bridge to get to the other side, say 20km away, not very far for intermittent use of my first 8.5Ah battery. But you don't specify your battery by the shortest or the average ride you take, you specify it by the longest ride you take say once a year, in my case 60km, beyond which I use a car or the bus. That was when I used the motor very lightly. Now, unfit after the pandemic, I use it more and think 45 to 50km will be about right on my current usage of the motor, to leave it half full on my return home, where I recharge it immediately and let it trickle for an hour or so after the light turns green; that is the most vital piece of information I have to impart. The battery will be 40 percent to half the cost of your electric installation, and how fast it is consumed is up to you, so take care in your calculation and when you start using it to give it all the attention it deserves.
The motor itself is not a capital asset: it is a consumable and you should treat it as such, and be prepared eventually to buy a new one, probably on a longer cycle than you buy a new battery (I think my case, where I wore out a motor before a battery, is an outlier because I'm so careful with the battery, and I knew from the beginning that the sacrificial motor was a learning experience; in fact I expected it to fail much earlier than it did.) Specifically, steel gears instead of plastic will last longer, and you should in your first month or so, or your first summer, check that the motor doesn't get abnormally hot. I haven't fitted the steel gears because I value silence a great deal and I'm not particularly trying to make my motor last extraordinarily long.
Ask if you need to know something more.
