Person who have not yet reached the highest, but practicing sadhana and have acquired some siddhis can intiate people?
In the most ideal situation, a Guru himself should be self-realized. Because, the end-result of all forms of initiation (DikshA) is Mukti or liberation and one who himself is not self-realized can not liberate others.
For proofs, we can cite the following verses:
SarvAsAmeva dikshAnAm muktih phalamakhanditam |
AvisheshAd bhavatyeshA prAsangikyastu bhuktayaha ||
The end result of all DikshAs is liberation. And, everyone can achieve the same without any discrimination. However, sometimes it can result in Bhoga (worldly pleasures) too.
BrahmAkAram manorupam pratyaksham swatanusthitam |
Yo na jAnAti chAnyasysya katham moksham dadAtyasau ||
How can one, who himself don't know about the existence of Brahman in his own body, liberate others?
KulArnava Tantram 13.120
Na NarenAvarena Prokta Esha Suvigyo VahudhA ChintyamAnaha|
Ananyaprokte Gatiratra NAsyaniyAn HytharkyamanupramAnAth||
BrahmaVidya should be obtained only from a Guru who is himself BrahmaGyAni. BrahmagyAna (or the knowledge of the Self) is not obtained from that Guru's upadesha who himself is not self-realized.
TasmAtattva videveha mukto mochak eva cha ||
One who is self-realized is liberated and he can only liberate others.
KulArnava Tantram 13.121
So, ideally a Guru should be having the knowledge of the self. But that does not mean Gurus who have not attained that highest state are not fit to be Gurus.
This can be understood when we realize that there are different kinds and levels of initiations. And not all forms of initiations immediately bestow Mukti.
They just mark the first step (or some intermediate steps) towards liberation.
So, likewise, there has to be different kinds of Gurus each suitable for each steps. For example, we have the following six preliminary types of Gurus:
Prerakah suchakaishchava vAchako darshakas tathA |
Shikshako bodhakaishchava sharete guravaha smritAh ||
Gurus are of six kinds-- Preraka, Suchaka, VAchaka, Darshaka, Shikshaka and Bodhaka.
KulArnava Tantram 13-129.
- Preraka Guru
From the word preranA (inspiration), One who inspires the disciple into initiation.
- Suchaka Guru
From Shuchana (indication)- One who, according to the disciples mentality and aptitude, indicates the correct (or suitable) path for SAdhana for the disciple.
- Darshaka Guru
One who shows the disciple how to perform the various rituals associated with the particular SAdhana and also who is capable of explaining their underlying significance.
- Shikshaka Guru
One who practically teaches the disciple the various rituals associated with the SAdhana
- Bodhaka Guru
One who inspires the disciple, and one who is capable of enlightening the disciple as well.
So, understandably, few such Gurus can very well do without being self-realized.
Also, DikshA is given utmost importance in all scriptures. For example:
VinA dikshAm na mokshah syAttaduktam shivashAsane |
Without dikshA there is no liberation-- This is Shiva's order.
KulArnava Tantram 14.3
Devi, dikshAvihinasya na siddhirna cha sadgatihi
Without DikshA, there is neither Siddhi nor Sadgati (liberation).
So, the act of DikshA is the priority for everyone. Now, in case, we are to take Diksha from only self-realized Gurus, then that means we all are likely to remain un-initiated throughout our lives.
Because, the number of such self-realized Gurus in the world can be counted on fingers, if at all they are available to us and most importantly recognizable.
So, IMO, it is not necessary that we impose such severe conditions on our Gurus. As long as we can verify that he is carrying the mantra or the knowledge from Parashiva (the Adi Guru) in an unbroken chain, to us, we should be ever ready to get initiated by him.
Besides, we should also check and test the Guru for signs (Guru Lakshanam). The Guru, in the same way, must verify some preliminary signs among the would-be-disciples.